"All posts read"

If this is already in, it's either not obvious enough or I'm REALLY stupid. There needs to be a way to know if I've already seen a topic or not, and whether or not there are new replies if I have (ideally, there would be a separate marker for new Riot replies.) It's confusing when I derp around for a while in subforums, go back to the "All" listing, and then a bunch of the threads I just read are on top but now theyre all jumbled around and I don't know if there's new content or what.