He didn't like it here for whatever reason, he could just have left.
No one would have noticed.
Why did he create a post?
Maybe to get people noticed but more likely because he wanted attention and discussion - that's the drama llama troll species.
He may not have logged in, but has friends to do so to post and give him feedback on what others posted.
To remove a drama llama just stop posting. Then it'd be too boring and he'd have to register again...
(Now I don't know any of the background of the story, but whenever someone has ANY complaint one should always complain to an admin or mod, even if the guy the complaint is against happens to be a mod). Posting such gossip in public is just to create attention.
Edit: and believe me when I say 'attention', it's a girl speaking...