Wow, that's way more advanced than anything I remember using back in the day. In my 300 baud C64 days, chatting online was done in full duplex mode, where ever

Wow, that's way more advanced than anything I remember using back in the day. In my 300 baud C64 days, chatting online was done in full duplex mode, where everything either party typed would appear on both screens at once, at the end of the current line. It's just a terminal, so there was only one place for the caret to be. You'd type your thing, then end with two carriage returns to signify that you were finished. There was nothing to stop you from typing out of turn, except that your characters would appear mixed in with the other guy's so that neither of you could read what either had written. It was just a social construct, typing into an input stream in turn. And it worked nicely. Fun times.