Currently, it is already possible to set someone on ignore. Go to User CP and on the left side, under Miscellaneous, click the link for Buddy / Ignore Lists. Paste the usernames you want to ignore, submit, and you're done. Note: you cannot ignore mods.
That said, while some people may certainly get on your nerves, I'd encourage you to find other ways of dealing with it. Everyone says something useful at some time or another, and it'd be unfortunate to miss out on such things just because you put someone on ignore. If what someone says infuriates you so much that you can't respond to them constructively, just hit the back button. No need for ignoring
I like to think that we're all mature enough that we can handle disagreeing with or being annoyed by certain people from time to time. That's life after all.
Just some food for thought.