I often compare one PDF to another, and the prev version will have lots of comments to make sure I address. To help myself keep track of where I've made it to as I go, I collapse the page's comment list as I complete a page. I really wish there was a small collapse bar with an up arrow/caret at the bottom of each page's comments list, since when I read the last comment about a page, I've scrolled quite a bit in the comments bar and have to scroll up again to collapse the page's list from the top. For ease of continuing, if I could collapse from the bottom of a long list of comments, that would make starting onto the next page that much easier/faster with no scrolling back up!