Can I filter notifications by content before they appear?

No, you can just filter by type of notification. In other words, you can put Messages in Notification Center but not Mail. You can separate Mail notifications by account, but that would be about it. I believe you would be asking if you could get notifications from SMS from person 1, but not person 2. Is that what you are asking?

See this support document about Do Not Disturb. http://support.apple.com/kb/HT5463. You can set that for Favorites, but it might help some. That would be the best there is. Notification Center does not have settings for that type of filtering.