I was asked to login concurrently from two different browsers, every time I wanted to login. It was a very puzzling experience, and took me a while to figure it out, because it was something I've never experienced before in chat systems, and it wasn't spelled clearly, like "you must login from two browsers", in order to compensate for the unusualness.

The UX of communicating with other users was problematic as well. I've tried to establish communications with a certain user, and I have no idea if I succeeded or not (likely not); two separate communications "channels" (I don't know the terminology) were opened with the same user, which is perplexing, since again, this is something I've never experienced before.

I think those two weren't even the only problems I've had.