What works well is to strike a balance between insight and rationality. Be logical, non-emotional, but have something interesting to say.

Moreover, personal experience seems to score well, in particular when it underscores your insight into the subject.

Take a look at the top comment on several current comment leaders:

https://news.ycombinator.com/item?id=17620543

https://news.ycombinator.com/item?id=17623104

https://news.ycombinator.com/item?id=17617825

Don't force it. Comment on topics you have genuine experience, interest or insight into. If you hit the right tone, your comment should naturally do well.

PS: With the number of HN users growing year-by-year, it gets easier to score those little dopamine hits...

I would like to know it too...