It was a weird one, I remember some of the details. It wasn't one long story, it was like a series of little stories.

1. Voldemort had some plan to assassinate Harry with a snake, but it didn't work as he intended. Harry was a snake animagus or something and Voldemort picked a random snake near Harry's house which turned out to actually be Harry.

2. Rita died in her beetle form, crushed by someone random.

3. Due to Voldemort's failed attempt at killing Harry, Harry developed some of the properties of the magical snake which resulted in him being able to sense gold. This makes him retardedly good at finding the snitch, so he quits quidditch because it's cheating. I think there may have also been something to do with making snitches out of silver so he couldn't track them.

4. While voldemort is doing his machinations to kill Harry, Harry goes missing and people assume he's been killed. Or something like that.

5. Having quidditch ruined for him, he has fun at some point by chasing after a snitch that's been improperly enchanted and moves much faster than it's supposed to. He uses his new talent to chase it down.

 

Also, it was a series of short stories. Sort of episodic, I think.
I think it was on skyehawke.

 

I think it's time for another shot at this.
Hopefully someone will recognize it.

 

The summary of this one seems close to what you are describing:

 

This sounds horribad.

 

Yeah, I don't think I managed to finish the first chapter before I put it in my "unreadable" folder. And that was years ago - it probably reads even worse now