That's what I want to know! As a rule, I don't usually accept requests from people I meet online, but if it's a friend code, I accept it, because then it's probably someone I know, but I had no prior outside warning, so I was hesitant to accept.
Here's something funny: I have two accounts on my Switch. My main one is named Mglor04726, and the other has my name on it. But my main one is linked to the email with my name in it, and the other is linked to the one with magolor04726 in it! Fun flip flop, I suppose.