I'm fairly certain it's true.

Here on YC News, even a minor comment a few lines long might get at least one or two upvotes (or downvotes). I'll get a reply about 50% of the time.

On Reddit there are posts with apparent huge volumes of "user interaction": thousands of comments, thousands of upvotes per top comment, etc... but if I comment on one of those posts... nothing. Zero up or down votes, zero replies, just... silence.

I'm learning to recognise these posts now, and they're the majority of the "front page" volume. The only posts where I'll get any interaction now is the really niche ones like the hobbyist ones or "owners of specific gadgets" and the like.