The answer is simple. I think these comments provide useful and important evidence for the state of the crowd's mind in the stock market. As I have noted in the post you can find here, a sure sign of a strong consensus about the market's future direction is the intolerance of people who hold this consensus view towards those who do not share their opinions.
I include some (but by no means all) of the comments of this type because I find them helpful in forming my own views and because I want to document in real time the intolerant nature of crowds.
You will notice that as soon as the market starts to rally comments of this sort virtually disappear from this blog. This happens because the people who make them only gain confidence when the market is going their way. And when they are supremely confident, as they are now, it is a good bet that a big reversal is at hand.
Added at 11:23 am: Note how quiet the comments section has become as the S&P has rallied 40 points from yesterday's low!