1. A higher bar for comments based on age of account and karma.
2. A limit on the number of comments from any individual account, e.g. each account would only get one or two comments. The idea being "get out your point as clearly as possible in one message", because you won't have the option for endless back-and-forth (and potentially escalating) debate.
But I've also personally used a couple new separate accounts to comment my experience & knowledge on topics that I wouldn't want to be google able to myself, even if I share that with my IRL friends.
Maybe there could be an option for 'private post' that you can still use your main account so mods can still look at coordination across accounts etc but the public facing handle is not tied to your public profile.
Probably would still encourage the type of comments most in this thread are against though that's a hard problem.