Totally. I'm kinda off topic, sorry. More the epic amounts of troll and fake accounts. I deleted my Twitter account at about 15k followers, the trolling and spam got too much. Point well taken! :)
I think he meant a paywall, kind of like how some services don't waste their time offering free accounts and receiving tons of support requests.
Billy Gates also famously pondered charging a fee for sending email to reduce spam.
Paying for an account also leads people to feel they're entitled to do whatever they like with it, which might be counterproductive to encouraging civility.
I’ve more commonly heard anecdotes to the opposite conclusion; receivers of free work often value it little and feel entitled to request improvements, while paying users value the service enough to pay.