Sorry for the forums trouble. This forum is based on Discourse, and it manipulates the browser DOM in a number of pretty advanced ways. I didn’t realize Safari was a problem. I’ll let others know about this but I’m glad you can use Chrome as a workaround.
Oddly enough, I use Discourse on other sites and don’t seem to have a problem. It isn’t clear why the threading and message display behaves so oddly here. I’ll keep an eye on it when I visit other sites that use Discourse and see if I can narrow it down.