I think this is an uncharitable view, and while it might be true in some cases it is certainly not always the case. Many times the people who point out issues with Signal do it not because they think they want to show off, but because they honestly are frustrated that no product seems to meet their needs and Signal has specific issues that matter to them. I honestly believe “Signal is stupid for relying on phone numbers and SGX” is really just “I don’t trust this things, they have a track history of having issues, I would really like to use this service and am sad that you chose to do this”. Hacker News is often not very good at conveying what it is trying to say, but I remain optimistic that it’s more than a intellect measuring contest.
I remember the outrage quite well when Facebook started spamming ads to the phone numbers of people who were forced to give Facebook phone numbers for "security" purposes and promised to never been shown ads on those numbers. Or when Jack Dorsey's Twitter account was hacked because of SMS 2fA.
Last, phone numbers are general identifiers used in the search boxes of various data collection tools. Maybe you can search by the Threema ID as well, but that requires the tool to be a tiny bit more sophisticated, and that means the people who like to invade privacy of are a bit more frustrated.
That isn't "smartness signalling" or whatever, that's a real concern.
The phone number was the only thing that was preventing them from keeping metadata such as usernames on their servers(until they introduced the PIN). It was a tradeoff between two concerns.
