I have a site that includes lists of 25 items, each one of which has its own comments block, and each comment can be linked to directly, in which case the page is loaded, scrolled to that comment.
Previously, the comments worked as follows: we'd show first comment, a "show more", then the two most recent comments. Show more would expand all of the intervening comments. If someone linked directly to a comment that would be hidden, we loaded the page with that comment block expanded.
The problem with this system was that popular items could end up with thousands of comments, and page loads would time out or run out of memory.
We replaced the old comment system with paged comment blocks, 5 comments per page, paging in place on the list page. If someone jumped to a comment in the middle, we'd load with that comment showing. Otherwise, we load the last page, with the most recent comments, for each item, which may have 1-5 comments.
This solves the problem with page loads crashing, but it is not popular with the users who were used to being able to see all comments at once, without paging. Is there a better pattern for handling showing/paging of comment streams?
EDIT: I should have mentioned this previously: comments often reply to one another, so the sequence of comments is important. We don't currently store threading data, so ordering by top comment would cause issues with following conversations.