it was on livejournal- they had a 10k comment limit on posts

it fell out of practice on dreamwidth because, while i believe 10k's still the upper limit, posts that got over 5,000 comments would cause undue stress on dw's servers and you'd get a nasty combo of captcha + constant server error messages that made it nigh impossible to comment

idk if they've fixed the server issue or not since then, but that's why wg and rpanons both tend to go for new posts at 5,000