My main account at Stackoverflow has just been awarded
Mortarboard badge (it happened as I received couple of upvotes for my recent answer). Problem is, I was nowehere near 200 reputation today, not even in past 24 hours (my initial thought why would that happen). I also checked my reputation history to see if there's a +200 change anywhere, but I can't see it. Is there a bug or am I missing something obvious in the way it works?
Edit: I went though my reputation page and there's no meaningful change coming from removed posts. Majority of changes is less than 10 rep, and those differences never occured during the days where they could cause 200+ boost. Badge is still here, which makes me think it is a bug indeed.