But if you want decentralization some options i can recommend are matrix,simplex,session etc.
But to be honest, there is a good point that you raise about how to talk decentralized on bluesky
well, one of the ideas that I can think of right now, is that someone can use https://keyoxide.org/ and paste in their public key and also connect both bluesky and matrix and then have the keyoxide as part of something public like a comment
The problem in this is that it becomes tedious and does add more friction to the whole thing but definitely possible.