My opinion about having a registered forum is that it's not needed. If Chris respects the limit of making only 20 HM's, and there's no reason to think he wouldn't , there's no way any of the hundreds of other Revomaze owners will ever see or own one. the people that have them now are unlikely to ever sell them. The only thing a registered forum does is hide the trials and tribulations of solving this rare puzzle from the rest of the forum. It's unlikely that any of the owners will give anything away in the registered forum if the other registered forums are any example.
Now an open forum is absolutely needed, of course.
If you guys want to exclude all other members from your discussions, fine, be that way. I think it diminishes the enjoyment for the other members not lucky enough to have ordered one.
If there are future limited editions, they should also not have a registered section. How would people feel about not discussing the Ti puzzle in open forum?
Really, what is there to lose from allowing the rest of us watch you guys suffer?