Humor is a little suppressed here, but after going to Reddit, I think that's a good thing. Otherwise, attempts at humor becomes disruptive to the conversation.
I found that no downvotes meant that people who disagreed ended up talking to each other the most (since you can't downvote, if you disagree you need to argue), leading them to become rivals and then friends. Actual synthesis of viewpoints happened.
Perhaps HN is too big for that effect and it would turn into chaos, but I'd be curious to see it tried.
Something like Lesswrong’s dual voting system of up/downvotes + agree/disagree may also help, but I’ve never engaged with discussions on Lesswrong to tell if this works on larger communities such as this one.
Comments get loaded with unpopular opinions, which is often things like the ineffectiveness of masks in stopping pandemics, or people who post evidence on how dangerous vaccines are. When someone dies, someone will post all kinds of slander about them. Because there are only upvotes and no downvotes, these float to the top, and the comments are usually counted as engagement, further boosting the comment.
A lot of the most commented on submissions were actually flagged/killed on HN.
It's certainly possible it would turn out the same way though.
1) Reduce issue-related downvoting by only allowing some random subset of the current active users to downvote, a different set per post. Don't let the user know their vote won't work in advance, but tell them after.
2) Reduce vote sockpuppeting by recording which pairs of voters downvoted a post, then disallow that pair from downvoting a post again. This includes votes that failed due to 1).