Today I got to 15000 reputation on Super User. I received the notification that I could now protect questions (eligible for protection as per the FAQ).
Interestingly enough, it didn't work. I just couldn't find the link. So I brought it up on Meta.SU.
It turns out: At exactly 15000 reputation, you can't protect a question. If you are at 15001, it works though. Probably the internal check uses a
reputation > 15000 check instead of
reputation ≥ 15000. Should be easy to fix.