That's not exactly possible.
He would have to implement a login feature so people could have unique identities.

When Mishima posts in the Anon Chat, he's injecting a unique post directly from the server.

So, basically, he screwed us over by making us think an awesome feature existed? Whilest toying with us by making whatever changes he thought were funny? What a zero.

Well, the whole incident was meant to troll the chat. It was only done for memes:

Looking cool, Joker!

Hehe. [innocent whistling]

"Screwed us over"
What self entitled bullshittery are you on about now?

It's posts like those that make me question why you're the leader