@vzn Well, if you have a look at the first day of transcript you will see that this room was created by some kind of bot and the first message was along the lines: Welcome to chatroom for MO...

So I thought it was reasonable to call this the main chatroom for MO. Perhaps associated chatroom could also be also a reasonable name?

In any case, several posts on meta.SO use the name "main chatroom". So I am not the only one who sees it this way.

hi MS the se chat system is full featured but not so prominent in the system. this is reflected in the way it has no effect on rep & also (currently) there does not seem to be active work on enhancements.

yes a se mechanism seems to create a single new chat room for each new site.

aka/labelled "main". however somewhat surprisingly if other rooms are created & that room goes idle (14 days), it can be frozen.

it appears the default listing of rooms is in terms of activity so there again if "main" goes idle wrt other chat rooms its listed later.