Alef:
I don't remember it from when I signed up, and I have spoken to a couple of non-commenters (not quite at 500 yet!) who registered much more recently, and who still don't recall the rule.
Currently, someone who has never commented or who has a views to comments ratio of greater than 500 to 1 sees a permanent announcement message encouraging them to comment. It's hoped that will be sufficient to remind them that the occasional comment is expected.
njrick:
And, of course, there are the many readers who DO comment every 400 or 500 stories, who will maintain full functionality, yet still provide little in the say of feedback. I can't imagine reading FIFTY stories without having something to say, let alone close to 500.
I agree that it seems incredibly little to ask that someone comment every 500 views as a minimum but the likely outcome of asking them to comment once every 50 or whatever will be a whole batch of meaningless "great story" comments and yet more attempts to re-register on the site each time they are required to make a comment.
njrick:
The question is - will this produce any more comments, or just fewer views?
Based on limited observations a number of previous non-commenters have started commenting, some genuinely, some merely cynically in order to get round the limit and about a dozen have simply tried to re-register under a different name.