It's the RMT bots way of avoiding the right-click > report RMT. It's so much more annoying than the PM spams before, in my opinion.

I'm just waiting for the right-click > report RMT to work with party invites too. I mean the name is on the chat too, why is it not part of an option?
For now reporting using the report cheater is what I've been doing to them lately. Their name is already a taboo enough.