Rehabilitate in case of a public (in the form of a forum post) admission of guilt and a promise to improve.
My opinion, which I adhere to not only in the game but also in life: Everyone deserves a second chance, but not a third. That is, if a person messed up, admitted guilt, and repented, then I don't see any reason not to give a second chance. Of course, this is not about immediate forgiveness, but the chance to improve should be given.
P.S.: I would play with Katerina myself, but only in 2013 :D