Also, when it comes to pinging other users, will the "@" work for both their display name and username or do you need to know their username for that (ie. can only ping
a username)?
Ah, okay. I think I didn't realize that because on mobile it just shows the display name and hovering isn't an option. (Though, long press will show the username, at least on my browser, because it shows the direct link to the user's profile.)
Might be different in apps, though, depending on how they interpret that data. I'll check that later, but not super important.