A lot of these look like misfeatures for a forum! Disallow replies is right out, adult content seems likely to be a per-forum social norm than a per-user preference, and while I can see your personal interest in a nofollow bit that’s not going to help the long-term health of the forum. There’s always pseudonyms…
HTTPS everywhere seems like a sane default but I don’t know of a reason to involve the user in that decision.