How does an accepted answer become unaccepted?

Question

Japanese destination airports with lower costs? (from US airports) had one answer, and it was a good one. A day or two ago, I added a little detail to it, and clicked to accept it. The green check mark did appear.

I went to that page today, click on some of the links, and it was not marked as accepted. I know I can un-accept, but I didn't. Are others allowed to do it?

I re-accepted it.

Answer 1

No, only you accept / unaccept answers of your questions, high reputation users and moderators can't do it.

So I assume that there was some problem with the website.

Answer 2

It looks accepted to me? You can un-accept an answer by clicking its checkmark again.

See also: Can I undo an accept?