A related issue is that comments on older posts are less likely to be read, and less likely to be voted on. Earlier comments are, on average, somewhat better comments (See one analysis of this here - http://www.marginalrevolution.com/marginalrevolution/2008/02/does-the-qualit.html ). But I still think the status quo is sub-optimal, especially when most people view comments sorted by popularity or in chronological order.

Now the fun part:

If this comment receives positive votes, how will that affect your assessment of its quality?