Related to: Well-Kept Gardens Die By Pacifism.
I wrote a script for the greasemonkey extension for Firefox, implementing less painful downvoting. It inserts a button "Vote boo" in addition to "Vote up" and "Vote down" for each comment. Pressing this button has 30% chance of resulting in downvoting the comment, which is on average equivalent to taking 0.3 points of rating. If pressing the button once has no effect, don't press it twice: the action is already performed, resulting in one of the two possible outcomes.
The idea is to lower the level of punishment from downvoting, thus making it easier to downvote average mediocre comments, not just remarkably bad ones. Systematically downvoting mediocre comments should make their expected rating negative, creating an incentive to focus more on making high-quality comments, and punishing systematic mediocrity. At the same time, low penalty for average comments (implemented through stochastic downvoting) allows to still make them freely, which is essential for supporting a discussion. Contributors may see positive rating of good comments as currency for which they can buy a limited number of discussion-supporting average comments.
The "Vote boo" option is not to be taken lightly, one should understand a comment before declaring it mediocre. If you are not sure, don't vote. If comment is visibly a simple passing remark, or of mediocre quality, press the button.
Is that bad?
Considering that some posts are getting hundreds of comments, not that many people have the time to read them all (especially if you have to search a bit to find what you have and haven't read), it may be better for everyone to have fewer comments, but of higher quality.
Or, to put it another way, considering that you're writing once to be read dozens of times, it's nice to your readers to take a bit of effort to polish up your prose, it costs a few seconds to you but can save a few seconds to a lot of people. This may feel unusual if we are used to situations like conversation (or online chat) where the listener/talker ratio isn't as skewed.
The real risk is when certain forms of comment (approval, disapproval) are discouraged, because the community's standards of "quality" are skewed.
It's not a matter of polished prose. I'm not paranoid because I think I might make a grammatical error or abuse semicolons. It's a matter of what ideas I commit to words and send out to the community. My thought process when I was debating whether to scrap my original comment was anxious and convoluted: "There aren't any other comments yet, do I really want this to set the tone for the entire discussion? This idea relies on the kind of personal anecdote that's gotten me poor results before. But it's still relevant, and I've been mistaken in the past about whether a comment would be well received..." At which point I decided that even if the original comment wasn't good enough, my internal agonizing probably was.