What would be your specific proposal? Members only forum? High karma only? invite only?

I should probably mention that this has been discussed before. An invitation-only mailing list was the proposal being thrown around back then, but some fairly reasonable-sounding objections were also brought up. I'm not sure whether the signaling problems of organizing (as pedanterrific put it) secret-society stuff outweigh the signaling problems of discussing the same subjects publicly (though I suspect the former is preferable), or whether either one brings a net gain over not discussing them at all (less sure about this one), but in light of the OP I thought it was worth revisiting.

After thinking about this a bit more, I think it's pretty clear that integrating a limited-access forum for sensitive issues into the LW site structure would be a bad idea; it's security through obscurity, not doing much to dissociate controversial opinions from LW in the eyes of the public or the media and almost certainly not secure against anyone determined to dig up such opinions. A less focused forum with the same access restrictions might actually be a better idea: it looks less like we're running a secret society and more like we want to keep our public-facing image on message. Private social forums are quite common on large websites.

That has its own problems, though, starting with the fact that we already have a Discussion section that does its job quite well, and that privatizing it would complicate outreach: a lot of people make their first posts on Discussion. A private mailing list run by people unaffiliated with SingInst or the LW administration might have most of the desired qualities, though; it could be kept low-key with little effort, pseudonymy relative to LW is easy to set up, discussions would be persistent, and high-karma posters on LW can say conversations are appropriate for the list without necessarily appearing to endorse its content.

Which is about what the first people to bring it up were thinking, but it's nice to have some explicit reasoning behind it.

I am intrigued by the idea of a high karma only forum personally, with the karma bar set just below wherever I am currently, of course.

In particular, maybe we'd be allowed to discuss politics in the high karma forum. The "no politics" rule is a shame, I think, because I'm sure we'd get something out of it. I understand that PITMK, but a high karma forum could get around that.