Participants list bug #1190
I'm not sure how helpful this is, given that I don't know how to reproduce it...at some point in my inverse.chat session, the participants list 'half vanished' - I could only see the left half of it. Closing/opening the list didn't help. I think refreshing or logging out -> logging in again was what fixed it.
FWIW I use Tree Style Tabs, which incidentally displays tabs horizontally to the left of the browser window. Perhaps this was a factor?
Firefox 62.0 (32-bit), Debian GNU/Linux 9.5 (stretch)