All of your Discussion Forum bookmarks for a given course will be available on the Bookmarks page. This page shows all the posts that you have bookmarked, organized by topic and category, just as they are organized on the My Discussion Forum page. You're limited to 200 bookmarks within a single Discussion Forum. The reason for this is to make sure that the bookmarks page comes up relatively quickly.
How to Add a Bookmark
You will be able to bookmark individual posts by clicking the bookmark flag (). Once you bookmark a post, the bookmark flag () will appear next to that post every time you visit that topic. You can remove a bookmark by clicking the same icon one more time.