> However, if you create consequences or a cost to commenting you'd eliminate toxic comments and trolling at the cost of less participation and an echo chamber (though, you could argue that not all participation is equal and you're mainly removing poor participants).

Twitter actually does this but only for some types of accounts. Every see the "see more" button under replies? That's where people of low quality go. Twitter has a sort of rating for figuring out if someone is of low quality or not and they usually get hidden. Even their likes and retweets get hidden.

Hasn't to help overall on Twitter though I have noticed I get less assholes replying to me.