[nottorp]

> There are some interesting concepts of "identityless messengers"

Like... icq... yahoo messenger... old skype... ?

And even some modern mobile chat apps i think.

[lxgr]

These definitely all had a stable identity (ICQ number etc.)

What I mean is having an ad-hoc identifier per contact/group chat which doesn’t allow your various contacts to correlate that you are the same person.