“I’d argue that wading through piles of dross is an even worse user experience.” — I think we’re on the same page here, and why we’re looking at solutions. You’re right that no barriers = uninformed drivel, and that’s what we’re both looking to solve.

Currently, no barrier puts the burden on the moderator. I think moderators can do more powerful work with their time. Your solution swings the burden to the readers, which I think is too much of a barrier, and an unfair one. My solution, I hope, is a barrier that puts the burden on technology, not the reader or the moderator.

As for the comment section’s location: there are a few ways around this. You mention some. But I think you can also do some on-page tracking to look for more telling behavior than scroll depth, like how quickly they scrolled. I’d rather not get too lost in the technology or measurement side, but instead identify the bigger picture challenges. Am I missing something that suggests it could hurt engagement? Is there an audience segment that contributes thoughtfully without having to read? Are there other unintended consequences? I’ll let web developers and product brainiacs figure out the how.