I understand how the system works, I'm just saying that the average content quality doesn't increase because you've ignored someone you don't like, a troll, or a meme-spouting idiot.
How so? Have you stopped the users from posting low-quality content? No, you've just ignored it, just like you probably ignored (by unsubscribing) r/atheism, r/gaming, r/funny, and all the other garbage default subs on Reddit. They were still bad, you just couldn't see them.
Well that was my point all along, you and everyone else who ignores them will not experience the poor content, but it will still exist. I definitely can see the ignore function being misused to ignore people who believe in different things than somebody. #politics will probably look like r/politics (i.e.: liberal circlejerk) after all the liberals ignore all the conservatives and all of the conservatives ignore the liberals.