> Signal can at least in principle censor user content, because they control both server and clients.
But given E2E and the Sealed Sender[0] functionality, they could only suppress messages based on the recipient's user ID, not based upon message content or the sender's ID. This all or nothing approach is a rather ineffective method of censoring – it basically just amounts to banning a user account. I wouldn't even call it censoring in the first place as that term, at least to me, refers to a more selective and refined approach.
> (And they do, for example you can "delete" your messages that are stored on other clients.)
This has nothing to do with censoring and nothing to do with Signal controlling "both server and clients". The Signal developers simply extended the protocol to include "delete" requests for previously sent messages. The client app still needs to implement the actual deletion, though. You could easily compile the Signal app yourself with that functionality removed and then nothing would get deleted from your message history anymore.
I mean, sure, 99% of users are not going to do this. But this is no different in the case of Matrix, where most people just download the default apps like Element from the app store.
So I don't even understand what your statement
> they control […] clients
is supposed to mean. Yes, they write the source code. So? Someone has to produce and maintain the source code and whoever does it will obviously be in a position of power. Producers are always going to decide what they produce. Consumers don't get a say in this – unless they become producers themselves (and in case of open-source software) adapt the product to their needs. Again, this is nothing new and is the case with Matrix, too.
But given E2E and the Sealed Sender[0] functionality, they could only suppress messages based on the recipient's user ID, not based upon message content or the sender's ID. This all or nothing approach is a rather ineffective method of censoring – it basically just amounts to banning a user account. I wouldn't even call it censoring in the first place as that term, at least to me, refers to a more selective and refined approach.
> (And they do, for example you can "delete" your messages that are stored on other clients.)
This has nothing to do with censoring and nothing to do with Signal controlling "both server and clients". The Signal developers simply extended the protocol to include "delete" requests for previously sent messages. The client app still needs to implement the actual deletion, though. You could easily compile the Signal app yourself with that functionality removed and then nothing would get deleted from your message history anymore.
I mean, sure, 99% of users are not going to do this. But this is no different in the case of Matrix, where most people just download the default apps like Element from the app store.
So I don't even understand what your statement
> they control […] clients
is supposed to mean. Yes, they write the source code. So? Someone has to produce and maintain the source code and whoever does it will obviously be in a position of power. Producers are always going to decide what they produce. Consumers don't get a say in this – unless they become producers themselves (and in case of open-source software) adapt the product to their needs. Again, this is nothing new and is the case with Matrix, too.
[0]: https://signal.org/blog/sealed-sender/