To me, that’s where the conflict that makes a Timetravel fic interesting comes in. My main problem is characters intentionally trying to keep the story on track as it happened. Like, what’s the point of you going back in time if you’re going to repeat everything.

But like you said, overestimating their own abilities and misremembering things would be a big factor in what drives a good plot forward.

In that million-word fic, “Fighting in the Shadows”, one of the things I actually liked was that the world resulting from Harry’s actions—all based on his ‘future knowledge’ and erroneous assumptions about the alternate universe he jumped into—is an objectively far more horrible world than the one in the books.

After more consideration, it does occur to me that “canon compliant” can also mean that the author isn’t adding things to the original that weren’t there in the original or taking away from it. In other words, that they’re making a good-faith attempt to keep the world as close to how it was presented in the books.

And that, I can absolutely get behind. Harry going back in time and fixing everything by getting the goblins to read the Potter will and then obtain his Griffindor/Slytherin/Peverel/Potter/Black lordships and single-handedly passing legislation in the Wizengamot would similarly not be “canon compliant”.

Which reminds me: it’s probably been mentioned before, but “lordships”. FFS. I haven’t been on Pottermore since probably 2006, and never got very far into it, so I’m not exactly familiar with all the extra info presented outside the books, but I always felt like Rowling was making a bit of a transparent jape at the Blacks’ expense by having them be “The Ancient and Most Noble House of Black”. When one considers that “Black” comes from “blacksmith” (along with names like, Gold, Green, and White, referring to goldsmiths, coppersmiths, and silversmiths), it stands to reason that the house of black probably comes from some muggleborn peasant in the 13-1400s, not some Noble Lords that go back to Roman times.