That doesn't seem like sufficient payoff, especially since there was no way to anticipate that meaning ahead of time. Also, that's not really something Harry forgot, more something he didn't even notice.
Whether it's "sufficient" is a matter of taste, I'd say. It's just sufficient enough payoff for me and avoids becoming ludicrously much payoff -- the Remembrall is a child's toy, afterall, not an ancient Artifact with DarkLord-detecting capacity. Indicating you neglected to do something (forgot to lock your door, forgot to apply your knowledge of physics) is more in tune with what I'd expect it to do.
More to the point it correlates heavily where locale is concerned -- the first broomstick lesson. So it's more likely that it indicates something near those events, instead of something in Harry's remote past.
- This thread has run its course. You will find newer threads in the discussion section.
Another discussion thread - the fourth - has reached the (arbitrary?) 500 comments threshold, so it's time for a new thread for Eliezer Yudkowsky's widely-praised Harry Potter fanfic.
Most of the paratext and fan-made resources are listed on Mr. LessWrong's author page. There is also AdeleneDawner's collection of most of the previously-published Author's Notes.
Older threads: one, two, three, four. By tag.
Newer threads are in the Discussion section, starting from Part 6.
Spoiler policy as suggested by Unnamed and approved by Eliezer, me, and at least three other upmodders:
It would also be quite sensible and welcome to continue the practice of declaring at the top of your post which chapters you are about to discuss, especially for newly-published ones, so that people who haven't yet seen them can stop reading in time.