But then would it be fair to unlike the poor person who's just got his/her brownie point?
By experiment, NT and I have discovered:
If the liked person happens to be online when a post is liked, they'll see the alert - if they look at the alert, then the red flash disappears.
They don't, however get an alert of 'unliking'.
If they haven't looked at the alert, and the post is 'unliked', the red flash disappears.
The number of 'likes' in their profile goes up, with a 'like', but back down again when 'unliked'.
So if someone didn't happen to be online, until after the 'unlike'. they'd be unaware of it all. And if online, they'd only notice if they were keeping detailed tabs on their 'like' count.
We can't check what happens if a like takes you over a trophy level, and then is unliked, as neither of us is near enough a level.