Consider removing the downvotes? Keep only the upvotes? Downvoting IMO feels bad for the poster. They stop feeling like participating. They might have very good and insightful posts which might not be popular. The downvotes end up driving them away and all you're left with is an echo chamber of groupthink
In a way, it does create an echo chamber: when the community consistently downvotes things that don't conform to X (in HN's case, X usually being "well-reasoned commentary relevant to the thread"), people tend to shy away from those things. One could consider the utter lack of response gifs on HN "groupthink", in the sense that everyone knows the community is unfriendly to them so they don't post them (even when they're funny).