It’s just a username, doesn’t represent anything special.
It seems like one of them default system usernames.
#Wierd username?
brisk talon
ember carbon
guy looks like a skid
elfin surge
if he isnt from 2016 He is a hacker/skid
That white shirt is only on old accs
Look at any rare username acc besides active ones like A
plush birch
Players didn't need to have a Rec Room account to play, but they were encouraged, that's what those profile pictures machines you may see in older versions are for, they're to create a Rec Room account, but otherwise you just played on your steam account. However it was changed and people who didn't create a Rec Room account, but played, were automatically transferred into one with all their items and a generated username. However, those usernames would usually be generated as @Guest-[3-5 Zeros] [Account ID Num][Other Numbers], in this case maybe their username might've been reset.
You maybe wondering why his character has that vest, I'd have to guess that it has never been active since 2016-2017 and since the UI wants to have their character that they've never changed, something bugs out and gives them this vest in the process.
Also, I can't seem to search for their account, neither the @ or display shows up on RecNet, which is odd.