I got a bad comment from a new registered user today even, so I deleted the user, and it said that when i do this all the users comments will be deleted as well, but his comment is still there. Nothing seems to work at all in managing comments.
I do have a user with no name, which is me from when i imported my posts from typepad. If I delete that user though I will likely lose many of my posts since I imported 154 posts from that.
So not sure what you mean as a ‘ghost user’?