Bookmarking Topics

It would be cool to be able to select a post/reply in a topic to 'bookmark'. So if you're reading someone else's topic, you can save your place if you can't read everything it one go. For example, if a topic is five pages and you're up to a specific part, you could 'bookmark' that specific reply so when you come back to the topic you know where you left off, rather than having to click through the pages trying to remember what have or haven't read yet. Especially if the topic has been replied to several times and everything has moved, and instead you could just click 'jump to' the post you last read. I think it would also be really useful in plot events, where you can go away for a few hours and there might have been 10+ more posts in it, and you're trying to figure out what happened since you last replied (and your post might be on page 17 now, rather than page 13 and clicking/scrolling trying to find it is a pain. So if you could just 'bookmark' it and you would be the only who could see your specific bookmark, so it doesn't intrude on other people's reading of the topic either. This is really badly explained but I hope it makes some sense.