Bookmarks is a super useful feature and personally I use it many times. I am thinking about a little plus which maybe can built in bookmarks.
Feature: Bookmark with selection. When you select a text in post there will popup a share and quote panel.
In this panel could appear a Bookmark option. So if you click the bookmark it will bookmark the whole post just like now but when you open bookmark it use the highlighted text feature which is now I guess use search if the text matches.
Maybe an anchor will be useful too which goes to the selected text in post when you open bookmark.
Benefits: Really helpful if users can separate a huge post to sections and bookmarks the relevant informations from it.