Here's probably the most underappreciated quote in the HP series:

One question about this quote is: did Harry master Occlumency here?

The quote is slightly ambiguous.

On the one hand, we have this:

This sentence would suggest that yes, Harry has mastered occlumency.

It explicitly tells us that Harry has learnt control, "the very thing Dumbledore had wanted him to learn from Snape". And of course, we know from OotP that occlumency is essentially about control:

And:

So Harry's ability to feel pain but not let it control him, to be above it, seems to match what Snape was trying to get him to learn in OotP: the ability to feel but be apart from it, to discipline his own thoughts.

The problem is the passage then goes on to say this:

This would seem to directly contradict the preceding sentence, saying that Harry's mind is protected by a one-time instance of grief, like with the possession in OotP.

How do you reconcile the two?

I think if you look at the passage as a whole, the impression is that yes, Harry has mastered occlumency. If Voldemort was merely being repelled by Harry's love/grief, as occurred in OotP when Harry thought of Sirius, then:

1. Harry hasn't learnt anything. The protective effect is a coincidence of his current feelings.
   
   
2. Control is irrelevant. The protective effect is a result of feeling what he is feeling, and control plays no role in that.

And yet the paragraph takes pains to say that Harry has learnt something (specifically, how to keep Voldemort from his mind as Snape tried to teach him to) and that control plays a role in that. Control is referenced twice: in the general ("he had learnt control") and in the specific (he felt the pain but was apart from it). If it was just the effect of grief, those references would be completely meaningless - not just redundant, but wrong.

So the musing on grief is to be interpreted as an additional factor, not the only factor at play. Harry has mastered occlumency and his grief repels Voldemort.

I think the rest of the passage backs this up. As Harry continues to dig, he seems to undergo some kind of enlightenment. He is making connections, understanding things, almost achieving a zen-like state. The overwhelming impression is one of a Harry who has undergone a mental transformation.

There is a follow-up from all this, which is the question as to whether Harry has also mastered legilimency. After this scene, on several occasions Harry deliberately dives into Voldemort's mind, and we know from OotP that the connection is a vehicle for legilimency. But perhaps that is a question for another day.

 

I haven’t got time for a long reply but I have long reconciled this as a manifestation of Harry’s ability and affinity for odd, emotional and subtle magics.

From your options, I also believe it is ‘both’, but via the vehicle of emotion. In this section, with consistent holding of grief, I believe Harry has learnt Voldemort will flee strong emotion. We also know that as the horcruxes are destroyed he begins to feel to Harry like ‘a wounded beast’. I imagined this made Voldemort’s interactions with a whole soul, feeling pure emotions, like Harry’s more challenging not less.

I think, in this passage, Harry has realised his grief and his dear pain for those Voldemort has taken from him, specifically the loss and the love, will keep Voldemort from his mind, and he can bring up those feelings quickly like joy for a patronus.

I think this plays to Harry’s strengths and his depths of emotion, while still gelling with JKs WOG statements about Harry not being able to compartmentalise like Draco and Snape and therefore not being suitable for occlumency.

I suppose I’m being cheap but yeah, I suppose: a Voldemort specific occlumency.

 

The very next passage seems to indicate that his grief subsides and he moves beyond it. Not that he's no longer feeling it, but that it isn't in control of him which seemed to be the fundamental tenet of occlumency as taught by Snape.

Specifically, "subsuming his grief in sweat, denying the pain in his scar."

I would posit that he did, in fact, master occlumency in that moment. As for legilimency, I hesitate to use the word master. He perhaps unlocked his latent affinity for it, but without some measure of practice I can't imagine he would be immediately proficient to the degree that, say, Voldemort was.

 

Well, to me, it seems that he has learned how to block out Voldemort. The problem is doing the same thing on cue for when someone isn't dying/dead.

I don't think Harry ever really understood what he was actually meant to do to to block out Snape in OotP. He knew he was meant to block him out, just not how. Here, he's understood it but whether he can perform on cue is yet to be seen.

 

Blorcyn's explanation makes the most sense to me. Harry has learned a very specific kind of control: the kind needed to keep Voldemort out of his mind. He can harness his grief or his love and use it as a shield against an intruder who is literally part of his mind.

Whether that method would work on any other legilimens is up for debate. If I recall correctly, Snape wasn't trying to read Harry's thoughts but sift through his memories. His 'control' with Voldemort--his zen-like state--seems to come from both learning how to separate himself from his pain and finally understanding Voldemort's weaknesses. I'm not sure I see how that would help him prevent someone like Snape from accessing his memories.

'Clear your mind' is so ambiguous. Maybe there are different kinds of occlumency mastery in general. One might allow Harry to stop someone like Snape by literally blanking his mind, thinking of nothing and giving him no foothold. The other might allow someone like Snape total control of his emotions, so he could lie to LV without getting busted. That ability might tie into creating believable false memories. The latter definition seems to be beyond Harry.

 

The tl;dr is that Harry learnt there how to take control of his connection to Voldemort, but I'm not sure how much it would extend to Occlumency and Legilimency against other people.

First he took control. It's quite obvious since it's spelled-out for us. Like after Sirius' death, he feels such overwhelming emotion that Voldemort can't stand to touch it, but unlike after Sirius, he isn't controlled by that emotion. Book 5 he couldn't think or feel anything else, but here he is able to think clearly about Horcruxes and the Elder Wand. The manual labor might help to enter a transe-like state, but in that moment, he is fully in control: the strong emotion keeps Voldemort at bay, but doesn't paralyses him. In a way, he has learnt to compartmentalize.

We see in the following chapters that he doesn't necessarily need the "help" of a strong grief anymore: he "wrenches himself to the present" after Voldemort kills the goblins, he ignores Voldemort through all the battle except for the few times when he checks where he is, and he can enter Voldemort's mind and exit it easily enough when he does.

This control is not perfect and quite strainful for him, as seen when Harry finally fails to prevent seeing Voldemort take the Elder Wand, or when he's surprised by his rage after the Cup, or when he can't help but see Snape's death by Voldemort's eyes. But in general, I feel it's safe to say that Dobby's death taught him the "key" to dealing with his scar.

Second part is how it would translate into Occlumency and/or Legilimency with people other than Voldemort, and it's much harder because we don't have any material about it from the book. Harry doesn't comment on how exactly he prevent Voldemort's from sending him images after that first comment about grief, so I think it safe to assume he keeps using his strong emotions to do it. The question is then how effective it would be against someone else.

We can't be sure, but I don't think it would be as effective. First because it was basically the opposite of what Snape asked of him (flaunting his emotions instead of hiding them), but it serves the same overall purpose (distracting from his current thoughts) so it might be doing the job. However, Harry's emotions (especially positive emotions about other people) are completely foreign to Voldemort, so they serve to anchor him and allow him to isolate the connection in his mind. And that would simply not work as well with normal human beings. I certainly don't think Snape for example is unable to understand or feel grief, so I don't see it being much of a bother for him.

All in all, I think he did manage to compartmentalize so it would serve against other mind mages, so it's certainly a step in the right direction, but I don't think his methode would be as effective as it is against Voldemort. Other people would already get information by encountering his emotions, and emotion wouldn't make them flee as it does Voldemort.

 

As I understand it, Harry was able to master occlumency, or at least get a decent grasp of it. Feeling emotions and yet somehow holding yourself apart seems to be part of it.

The only question that remains is whether it was solely Voldemort centric or not. I mean he was keeping Voldemort out passively during the final battle until Hermione urged him to let him in so that they could find where he was. But whether it will work for any other Legilimens... well can't say conclusively either way.

I personally believe that Harry got a handle on it.

 

I'd go with both in the sense that he has developed voldemort-specific occlumency as well as general occlumency. Voldemort is completely shut out unless Harry lets him in.

 

If I'm not mistaken, he allows himself to receive visions through his scar that he had been blocking out during the battle at hogwarts. But that to me would suit Taure's suggestion of Legilimency rather than Occlumency, given that Voldemort wasnt trying to get him to see that stuff.

 

Aha, I remember we had this discussion a few years back! I would say he did master it in that moment.