Rando Red Flag:

some guy I knew

MSN Messenger Red Flag:

on msn messenger

Emotional Dysregulation Red Flag:

He got really upset

Histrionics Red Flag:

ranted about people only reaching out to him cause they needed their computer fixed and never to ask how he was doing

Provocateur Red Flag:

is the red flag "man expresses loneliness and frustration"

Truculent Red Flag:

is that the red flag

Malicious Actor Red Flag: Username using template that is very easy to script for automated bulk account creation. For instance, something that combines a random word with a random number.