I sent an email to the developers and they said there were many issues with Invision forums and listed a whole range of the causes - one of them was the rich text issue which you fixed, but there were several others some of which were very technical and beyond my understanding! However, they did suggest trying another browser, so I went back to my Chromium browser for predec (I also use it for banking as it doesn't involve the very irritating 2FA thing where you have to get a 6 digit code on your phone).