You don't keep your job under this administration by sticking your head out.

He was one of many initials present at the beginning of the chat, no?

No, it said just "19 members". Nobody would notice him unless they went to the group settings, or he spoke up.

https://archive.is/YmtqQ/bb4da26bd1dd20371c772ed26070f066358...

Signal just released a change that lists all the members in the chat itself. You can guess why ;-)

https://github.com/signalapp/Signal-Android/commit/da3fc408f

No. To the others he would have appeared as a random number.

He would appear as whatever he set his profile name to.

He actual specifically says this in his article.