Regarding your Mortarboard badge, here's the relevant snippet from the official Badge FAQthe official Badge FAQ:
The site admin has stated multiple times that, by design, badges cannot be lost or revoked. There are two exceptions to this rule...
Basically, what happened is:
- You hit the rep cap at some point before the recalc.
- The mechanism for awarding badges saw that, and credited you Mortarboard.
- After the recalc, you dropped below the cap for that day.
- Since you didn't actively cheat, you get to keep that Mortarboard forever
- But, the day for which you were awarded that Mortarboard for will not count towards the Epic or Legendary badges.