Comments are for a brief request for clarification or improvement, and they can be deleted after the querent or respondent performs appropriate edits. If sufficiently sure of yourself, a witty Bon Mot can be added, though it's likely to be swept up in general purges if not highly upvoted.
Comments can be unhealthy so they tend to get cleaned up quickly — arguments are very easy to have about role-playing games. Responding to a comment is almost always not worth it, as it takes effort that can otherwise be used to improve a votable resource.
Especially unhealthy usage of comments includes: starting an argument, leaving a comment on an answer only to tell them they're wrong and/or their answer's bad whilst suggesting no means of improvement (just downvote, and if you can, provide a better answer), or thanking someone for their help (just upvote), or asking them about entirely unrelated problems in comments (this is help vampirism; you should start a new question instead so people can use the proper answer mechanisms to respond).
Invite people to chat to have debates, so that only people who want to voluntarily subject themselves to the argument can see. (You can use
[chat] in comments, make your own room, or link to the main rpg chat room.)
The intention here is to focus on improving question and answer quality. Conversation is for chat or a forum. And unfortunately, comment policing isn't something that can be done halfway, as hanging comments tend to attract arguments and discussion and thereby decrease quality.
It's also worth noting that much of our deletion prompts come from commendable user flagging of comments that have become too chatty, argumentative, or correctly have been edited into their respective posts.