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.