John Dallman
Hero
With a little experience, such characters are easy to recognise. There's hardly any need to persecute them: their players usually can't handle them effectively.However, neither allowed brining in a character from an external group. I think this comes down to play style but there was also some concern about whether an imported character had been just written down or been played.
The club where I first encountered it was a university's Chess and Wargames society. You needed to be organised as a club to book rooms in university buildings. This club predated D&D, and role-playing had budded from the wargaming side.The commonality I'm seeing in those who did so is that they were playing in clubs. Specifically, D&D clubs.