I wonder whether they are shown for all users. Namely are they shown to unregistered? Are they shown if a user which does not have sufficient reputation to use chat views the site?
Yes, the chat rooms are displayed in the sidebar even to users who can't actually chat:
This is consistent with many other things that are visible to the user, even if they can't do it:
- Add comment
- ...and more
In my opinion this is not bad, this way the user can learn about the existence of chat, even join the rooms, and when reaching enough reputation, take active part.