It's true but I'm in same boat as parent: I only downvote on spam, hate comments, etc. Downvoting can make comments disappear and sort of censor aspects of a discussion. Even bad claims are often misconceptions worth addressing with comments and evidence instead of downvoting for other readers' benefit. So, I almost never downvote.
I'm sure there's others given I know specific people's position on comments I made that they could've downvoted. So, parent's claim stands but we can't know how much. Maybe worth considering modifying downvote concept to deal with this somehow in another forum as an experiment.
My view is that there is a ton of noise of HN, and HN has this problem where threads devolve into tangents/pedantry/really nitpicky arguments where people start arguing over little logical details. And rather than just go down the rabbit hole of this morass of noise, I'd rather just downvote.
Sounds reasonable. A third option you don't mention is simply ignoring the noise to upvote the quality submissions. You apparently had to look at the noise anyway to downvote it. So, is there another reason you're taking that effort?
I'm sure there's others given I know specific people's position on comments I made that they could've downvoted. So, parent's claim stands but we can't know how much. Maybe worth considering modifying downvote concept to deal with this somehow in another forum as an experiment.