Have you ever been in the thumbshare forum, there are places where you can post other people's work that you think deserves more exposure. Posting thumbnails of others pieces on this site does not violate the rules. In fact it is the purpose behind the existence of this site, an art sharing site. Further, don't complain there is no credit to you, unless someone is stupid, mousing over the piece displays all relevant information.
Now if he had copied the piece and submitted it into her own gallery then it would have been violating the rules. But posting another piece on in a comment is free game. If you didn't want it to be seen in the first place, why did you submit it. Common sense.
Because I had literally no idea it would possibly be use for this kind of purpose. It's defamatory and, as I have stated multiple times now, goes against the TOS in two different ways. I had every right to report it and if you don't agree with it then you can choose to ignore it for all I care.