Supposedly, the Disciplined badge is awarded if one,
Deleted own post with 3 or more upvotes.
Today I was awarded this badge, without deleting any post myself. However, some question (I think this one...) to which I posted an answer with four upvotes, was deleted by someone else. I don't think that I should have received the badge, since it was not me who was disciplined (somebody else made the call).
One could also argue that this is intended behavior, but in that case the badge description should be updated.
Update: Three hours ago Jeff tagged this as
status-norepo. Then Shog9 tossed in an hypothesis. Perhaps we can reproduce this behavior by following the steps outlined in that post. (Or somebody could just check the source code, but where's the fun in that?!)