I don't know if this deserves its own topic, since its so minor, but I still feel the need to point it out.
So, this is a weird thing I noticed by accident. So, when someone likes one of your posts, it shows up in your notifications, right? Well, recently, I happened to be looking at one of my own posts (not actually looking at it, but it was on the page) when someone liked it. Less than a second later, they un-liked it. Then the post was liked again (I assume by the same person) all while I was on the page. It showed up in my notifications the first time it was liked, then disappeared when it was un-liked, but the second time, it didn't show up at all (I checked, too). My notifications gave no indication it had been liked until someone else liked it later. I would have had no way of knowing until then if I hadn't noticed it.
The whole liking system in general has always seemed glitchy to me, but this stood out. I don't know if it had to do with me being on the page, or the whole like-unlike-relike thing.