I do not even know what the problem is. Being able to create as many accounts as one wants? How is that used for "command and control" though? I am missing something here I think.

I don't see it either.. maybe a Signal employee posted this comment to try to justify phone number collection because they can sell those at a premium (or a secret order from the Gov. forces them to do it).

Also, what I want is accounts protected solely by username and password (actually, just a 50 character password without login would satisfy me)... this is one reason why I am slowly moving away from gmail. 2FA doesn't help me because I use my own device to login and if they get compromised, I am screwed either way.

i call this a bs strawman. this is just nonsense because as you said, element and email are perfect examples of decentralized networks. you also have fediverse that woks on trust between a local network as well as any trusted servers, still that system doesn't just explode.