I have tried refreshing and everything, but I still can't get rid of this so am starting to think that this is server-side rather than me (and many others are saying that hey have it too):

And it is not just the chat rooms, the whole SE chat site is messed up...:

I am running Firefox 41 on Ubuntu GNOME 15.10.

Information Update:

I am also noticing similar problems on this site (where I am posting this question).