I think the karma system on reddit had a real effect on behaviour. What you often found it did was cause people to write comments for the audience of voters instead of for the person they’re responding to. This eliminates personal interaction between users and turns everything into soapboxing. You stop having real conversations with each other, instead it becomes about pandering to votes.
This then also causes people to vote based on this as well. “You’re not saying what the group wants to hear” downvote is the voting behaviour it creates.