Oh I was looking at this part
"You agree to not use the forum to submit or link to any Content which is defamatory, abusive, hateful, threatening, spam or spam-like, likely to offend, contains adult or objectionable content ,".
I don't know about illegal but or sharing screenshot,which I would assume would extend to sharing a link to the Steam Store page which may or may not have NSFW screenshots of the game.
I can see a NSFW (Steam adult only game) as being something that is likely to offend some and that it also contains adult content (I'm not sure about the objectionable content part though).
So would taking about something like Senran Kagura and DOA be considered okay? Or at least to talk about that one game Eroge game that the Senran Kagura artist has taken a part in?