It's not a perfect echo chamber as you can browser /r/all and see and contribute content from/to both communities.
I truly miss the open forums (and even IRC, although that tended to be more focused) of the late 90's early 2000's yeah they could get vile some times but that's a bargain price for getting a public forum in which anyone can express their mind no matter how "wrong" or "offensive" some one can perceive that opinion to be. Today we get people claiming getting PTSD over twitter and every online community adopting a COC which often leaves no room for discourse that would make some one uncomfortable all and all forgetting that ideas that make some one uncomfortable are the ideas most worth discussing. 60 years ago it was "uncomfortable" for way to many people people to hear that blacks should be allowed to use the same bathroom as they are and thank cthulhu we didn't had Twitter and Reddit back then.
An obvious first step is removing downvotes so you can't completely obliterate someone who crosses sides to try to have a conversation, but after that, what else would help?
In my mind, some kind of code of conduct would help further those conversations, because it doesn't prevent people from expressing their opinions, it just makes them express them civilly. And if they express an opposing view without being overly antagonistic, then hopefully the other side wouldn't start insult slinging, and if they do, then that's what the COC would be there for.
I think there's a difference between having a "wrong" or "offensive" opinion, and expressing it in an offensive way. Do you think there's a way to achieve that balance, so that people can feel comfortable to express their opinions on either side, regardless of right or wrong, without it devolving into mudslinging and pure animosity on both sides? How do we accomplish that?
People mistake being challenged for being offended, having a discussion especially on a polarizing subject isn't supposed to be comfortable, but sadly we have too many people that have been cuddled to believe that it's their right to only hear the choir of angels reinforcing their opinions.
Heck even if some one decides to make a comment about ones maternal employment preferences I would not see a reason to moderate that, because unless you are discussing prostitution it most likely has very little to do with the actual argument and so would not score one much points in a debate.
Skilled debate in a venue like Reddit requires an understanding of esotericism, of not simply laying out facts and implications based on your own assumptions, but presenting a fascinating puzzle to the reader that leads them to challenge their own assumptions without being challenged by anyone in particular. When successful, such a puzzle glides beneath the surface tropes of the discussion, presenting the perspective without provoking hostilities. The karma system does not reward this very well, as those carefully crafted puzzles tend to get middling scores, while simple agreement, rationalization arguments(why your assumptions are right and the critics are wrong, from Someone Smart), and congratulatory joking trigger the instant upvote response. But putting in the effort into that dialogue is essential to engaging the community.