I'm pretty sure that Hendrik Vogt had already earned the mathmode bronze tag badge (and was the third user to do so after Stefan Kottwitz and TH.). A few days ago, his "mathmode" badge disappeared -- presumably because it was revoked after one of his answers tagged with mathmode was voted down and his upvote/downvote score fell below +100. Since yesterday, Hendrik Vogt's mathmode score is (back) at +100, but his "mathmode" badge hasn't reappeared so far (although new tag badges have been awarded to other users). Please shed some light on the matter.
See the rules here:
If you hover over his mathmode tag in the user profile you will see:
"Asked 6 non-wiki questions with a total score of 52. Answered 19 non-wiki questions with a total score of 101."
So he is one answer off from the badge.
Tag badges are the only ones that are taken away regularly, by the system, due to people no longer meeting the requirements. My guess is that a retagging happened that caused him to no longer meet the requirements.