It's impossible to make a personal attack against a nameless GUEST, any more than it's possible to make a personal attack agianst someone who writes an anonymous letter.

For example: "GUEST is a really interesting person who says interesting things, and I wish whoever it is would stick around and adopt some kind of handle to make communication easier; on the other hand GUEST is an objectionable little swine, and I wish whoever it is would just get lost."