It's no coincidence that the censored but not surveiled space is empty. You need surveillance to be able to implement censorship.
Discussion
Why are Signal and Telegram outside the surveillence circle? Or are they on the edge?
Signal is are to monitor as there is little to lool for but Telegram is mostly centralized and unencrypted (at least not e2ee).
Matrix has also a lot of public channels, even of encrypted they can be easily monitored as well.
Signal and Telegram are on the edge. I lack enough info, but from the recent interview with Pavel Durov I believe Telegram does have a degree of censorship/moderation. More importantly the company had to exit Russia end the US to remain relatively free... but that is unlikely to last long term. Since it's not FOSS, we cannot know ho much surveillance it has.
Signal is run by a foundation, but again there are many doubts about how private it is.
I guess it was correct to have doubts about Signal...
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