When viewing any room now on MSE chat on mobile device (or desktop with mobile theme), I see the following message:
Or in text:
This room is read-only
While this is technically true (it is read only for me since I'm chat banned), this implies the room is in gallery mode, so nobody (other than RO and approved users) can talk there.
The full site theme already has a friendly and useful message instead:
Can this message be applied in mobile theme as well?