>If you're required to use ID to get a SIM (as K2L8M11N2 stated in the parent comment I replied to), then what I was saying follows
Yes, and this is what I was responding to. You want that "if" to be taken for granted as an unchallenged starting premise to your entire argument. And that amounts to a massive privacy concession. And the fact that I'm challenging that premise, and bringing up the privacy concerns that are associated with that "if", that is the thing that you're describing as uncharitable. Even though you don't appear to dispute that it is indeed a privacy concession. And it only follows if you don't contemplate alternatives to using a phone number, which is what I took to be their point about the problems associated with a phone number.
>and more about what can be turned over if a user's device is compromised. In that context the name to number connection is more serious because they also have the content.
That's going true in any context where your number can be revealed, which is why it has unique disadvantages that usernames wouldn't have, under any conceivable hypothetical scenario. I'm glad that you benefited from their clarification but that struck me as a truism about the nature of phone numbers versus the nature of usernames.