Replying to Favourites

I'm not sure if this has been done before, or if this would be possible, but I would love to see a favourites system. Something like what YouTube does where you can favourite videos and then they show up in your own personal playlist. Rather than just videos, you could also favourite threads and pictures and whatnot by clicking the favourite button that could be beside the share button or something. I just hate having to search up old videos that I want to watch again, and with this system you could just go to your profile and watch all of them on a playlist.

Just a suggestion, and again sorry if it has been suggested before.