I have asked this question, how to do a secret handshake that reveals common membership of the group without giving away your membership to non members, several times before, and not been happy with the answers, so I guess I am asking it badly.

I will try to be clearer about the problem I am trying to solve.

These days, people no longer communicate on Usenet and email lists. Rather they use something for which we have not formed a word. I will call it a social blogging platform, unless someone has a better word.

Twitter, Facebook, and to a lesser extent WordPress, and such are all examples of this.

In a blogging platform, you post and people comment on your post. WordPress is the classic example

Plus, it is a communication medium, you can chat privately to people and groups, like viber.

Viber and skype are messenger with very little blogging, WordPress is blogging with very little messenger, Facebook is the two integrated. Viber is currently the best messaging system, WordPress the best blogging, Facebook the best integrated messaging and blogging system, but the world is moving to tighter integration.  Every messaging platform is adding some blog like features, every blogging system is adding some messaging type features.

Facebook consists largely of chicks posting "look at me, I am hot", boys commenting, "yes, you are hot", and then they go into Facebook messenger, communicate privately, and make an assignation to have sex. It was designed from the beginning for the purpose, hence the excellent integration between the posting and commenting, which is analogous to WordPress, and the private messaging, which is analogous to skype. Facebook is pretty much Skype+WordPress, and all the others are competing for the same market niche, though Facebook totally dominates the sexual assignation and booty call niche by far.

Specialist systems, for example the Cupid system for international dating have the same basic architecture - posts plus tightly integrated private messaging.

The trouble is that the major systems, especially twitter, are heavily politicized and censored, and so people are forming alt-tech, such as Gab, to escape from politics and censorship.

If you want to read a science paper about the nut gathering activities of the gray squirrel, or an adventure comic about the Mighty Thor, or a science fiction story about flash Gordon traveling to the far stars, you instead get politics.

You think you are reading about the nut gathering activities of the gray squirrel, and it turns into the effect of global warming on the gray squirrel, which effect we are told is extremely bad, though no concrete evidence of this is provided, the evils of global warming upon the squirrel being asserted but not actually shown.

But it is not actually about the effect of global warming on the gray squirrel, rather it is about global warming itself. We are told that global warming is even worse than we thought, though how bad we used to think it was is never precisely specified, and how bad now we think it is not specified either, and the evidence that we should now think it even worse is alluded to rather than given.

But it is not actually about global warming itself, rather it is that the industrial civilization that white people created is destroying the earth.

But it is not actually about the destruction of the earth by white civilization, rather it is that heterosexual white males are horribly bad, and extremely harmful to all other kinds of creatures.

Similarly, when one read the adventures of Thor, one encounters female Thor.  But it is not actually about female Thor, it is that gender binary is false and evil.  But it is not actually about gender binary, it is that ... heterosexual white males are horribly bad, and extremely harmful to all other kinds of creatures.

And similarly, when Flash Gordon travels to the far stars, it turns out that an evil corporation run by white heterosexual patriarchal males is oppressing blue skinned tree living aliens to steal their natural resources ... bad, and extremely harmful to all other kinds of creatures.

This endless insulting, ignorant, stupid, and offensive hectoring happens all the time, everywhere, on every topic, in every medium, on every platform, from Facebook to Twitter, from Scientific American to Marvel comics, from romance novels to first person shooter games, and if you complain, you are racist, sexist, homophobic, Islamophobic, and a denier and you get banned.  Observe for example that the only people allowed to be good fathers on television or the comics are blacks, and even black males are still required to have broken families.  Evidently the depiction of a good father ruling over a happy family is homophobic, bastardphobic, sexist, racist, whatever.

Recall that the movie "Man in a high castle" used a happy intact family on its poster as a symbol of Nazism. https://www.cinematerial.com/tv/the-man-in-the-high-castle-i1740299/p/iyn0japz

We are so accustomed to being lectured, shouted at, and spat upon that the shouting is felt to be normal and non political, and any easing up of the shouting and the spitting, as for example a science fiction writer who gives us a science fiction story rather than a lecture, is deemed to be extreme right wing politics.  If you hoist an umbrella against the spit, you are a Nazi and you are planning to murder the Jews.  And you probably really are a Nazi and probably really are planning to murder the Jews, because only really hard cases like actual Nazis planning to murder actual Jews are willing to defy public opinion by hoisting an umbrella against being spat upon.

To deal with this problem, people are developing alt tech, for example gab.ai, which is Twitter without mandatory left wing propaganda all the time on every topic.  Similarly 8chan is a reaction to the endless tedious left wing agitation and fierce censorship of 4chan

The most interesting conversations are happening on secretive invitation only sites, because it is only safe to say true things on a secretive invitation only site.

So, what I am thinking of is a way to integrate secretive invitation only sites in a messaging network of public sites.

It would be nice if when you clicked on a commenters id, you got a link to his posts, and to his comments on other people's posts - but if some of these posts and comments were on invitation only sites, you would only see those comments and posts if you were able to browse those sites, if you could have seen those comments and posts without necessarily following the link, and, more importantly, only be able to detect the existence of such comments and posts if you were able to browse those sites.  Even if you were using special software, not the regular client but a hostile client, you should not be able to detect that the commenter posts to secretive websites, or that such websites exist.