[Zedseayou]

I'm not sure what the behaviour is now but certainly the default a while back was that anytime someone in your contacts joined Signal you would get a message. Imo this was a crazy behaviour that immediately told you something about certain people in your contacts in a very visible way (that they were on Signal). I couldn't tell from the settings whether this was now off by default.

[amenhotep]

Telegram has done and may still (I don't know personally) do the exact same thing. Stated noncombatively and without assumption about what argument you may or may not be making, but seems relevant to mention in this context. Astonishingly bad behaviour no matter which app!

[OSI-Auflauf]

Both do that.