Excluding reposts and reshares, this sounds like an interesting idea. But without marking each post as "seen," how would you differentiate between posts you scrolled past, but didn't actually "see," and ones you no longer wish to see?

The only other way I can think of off the top of my head is an auto tag that happens when you actually tap on the post or view it for a certain amount of time, but it doesn't sound convenient to have to tap every post you don't want to see again so you will never see them again.