Optional
Optional... unless there's a service offered by the forum involving any type of trading/escrow/etc, required if you want to use those services.
It just requires forbidding users without 2FA to use those services.
It also depends on the 2nd FA used. I don't know many of them and I don't like the only ones I can think of (sms, yubikey) but maybe I'd like some other ones. Is there a list?
This isn't the thread to talk about why something hasn't been added to the bitcointalk.org forums.
+1 (sorry jackjack).
I think you quoted the wrong part of the post. If not, I don't get it.