Signal actively bans 3rd party clients implementing their protocols,

I agree with most of your points, but I'm not sure this is an accurate description. Moxie asked LibreSignal not to use their servers (and use the word "Signal" in their app name), which I think is silly, but I'm pretty sure there's been no code implemented to actively block 3rd party clients.

LibreSignal chose themselves to adhere to Signal's request, which I don't think they should have, but there's plenty of Signal forks and alternative clients around using their servers, signal-cli being one.

But Google shouldn't be able to demand you use Chrome on their sites, and Facebook shouldn't be allowed to shut down sites called anything with "book" in it, like failbook, and similarly Signal just shouldn't be able to demand this.

(I'm currently working on an alternative Signal client for desktop, built on top of signal-cli.)

Signal publicizes everyone's phone numbers in public chatrooms, so perfect strangers can end up harrassing you on the phone just because you were in the same room as them

Signal does show a dialog box when being invited to groups though. Does Signal even operate with the idea of "public chatrooms", like Telegram does? I thought there was only groups, and groups v2 with video chat.

Harassment calls can be an issue. Many phones support sms / call blacklisting, and Signal supports blocking.