I probably spend too much time commenting on blogs. After reading I react. After reacting other people react. Often I get drawn into this discussion. I feel like I am doing a good job wisely and sensibly responding to error and misunderstanding. I feel like I have a chance to present the gospel, use apologetics and unearth people's preconceptions about the nature of God and Scripture and truth. Sometimes these conversations go well. We end up at a point of understanding and mutual learning. Other times people attack rather than deal with arguments. I don't do this...but often I want to.
Here is some Scripture to inform how we should post, because as Christians our posts should be different. They should be redemptive and true.
"Let your speech always be gracious, seasoned with salt" (Col. 4:6).
"By your words you will be justified, and by your words you will be condemned" (Matt. 12:37).
"Love one another with brotherly affection. Outdo one another in showing honor" (Rom. 12:10).
"Let no corrupting talk come out of your mouths, but only such as is good for building up, as fits the occasion, that it may give grace to those who hear" (Eph. 4:29).
Speak the truth in love (Eph. 4:15, 25).
"If anyone thinks he is religious and does not bridle his tongue but deceives his heart, this person's religion is worthless" (James 1:26).
Scripture passages From http://thegospelcoalition.org/mobile/article/justintaylor/being-a-better-blog-commenter
This article has more wisdom on commenting as well, for those of you who have found yourselves in my shoes.