I am pretty sure anonymous is the automatic thing that your website does when an answer is turned into a comment and there was a comment on that answer.So if I answered something but a it was supposed to be a comment and someone commented on it.Then if one of the editors turned it into a comment, then comment on that answer will then say edited by anonymous.
I thought of this when sf answered(but it was supposed to be a comment) my question about arena trap, then I wrote down as a comment that I didn't know that, after that Trachy turned sf's answer into a comment, next my comment said that it was edited by anonymous.Information here:http://pokemondb.net/pokebase/meta/1175/arena-trap-information
Yes, you are right. I only just figured this out myself, probably on that same question too.