I happen to think the ability to ignore another user would be an excellent feature. It would not only encourage people to think more about their posts before saying something stupid, but it would also let people filter out those who contribute nothing positive to the site. I do, however, have some suggestions. I'm not sure how difficult it would be to code this stuff, but here are my thoughts:
When you decide to ignore someone, you should have a choice between having all their posts completely disappear, or simply auto-hiding them similar to the way tilt warnings currently work. If you choose to auto-hide, you will still when an ignored user posts something, but you will have to click on it if you want to read it. I also think that if you are ignoring someone, if anybody quotes them, the quote should be hidden as well. For example:
Quoted from gweempose:*IGNORED USER*