if you try to accept an answer not asked by you it gives the error message:

Sorry, only moderators or original author of the question - < author > - can accept or unaccept the best answer

Where < author > is actually the name of the user who posted the answer you're trying to accept, and not the name of the user who asked the question.

For example, if I try to accept my own answer on a question asked by Tom it says:

Sorry, only moderators or original author of the question - Leonardo Donelli - can accept or unaccept the best answer

Instead of:

Sorry, only moderators or original author of the question - Tom - can accept or unaccept the best answer