A2K has an instant chat? Since when?

It's only (relatively) active when a2k's server(s) are temporarily kaput. That's usually when I go there anyhow. When the server is down, usually Robert or another admin puts up a temporary error page that gives the chat room address and an apology about the downed site, etc....

is it different from the one that was there years ago?

It looks like its formatted differently then in previous variations. Cleaner and a bit more a2k aesthetic like.

we used to have meebo chat here...

That makes sense. Oh the memories.... ((looks off into the vague distance))