I find that my comment scores are higher and my comments more civil if I delete some of the comments I make. These days, I tend to write it, read it, then half the time delete it.
What you might want to do is give the commenter themselves a signal, more explicit than just a bad score or being grayed out. A message could pop up by the comment saying "likely to be downvoted, you are advised to delete this" - and see if more self-policing helps.
Also, if you have some signal that occurs before votes or other comments show up (like a lot of eyeballs on a comment with no upvotes), then maybe you can use that to give users an early signal to delete their comment.
What you might want to do is give the commenter themselves a signal, more explicit than just a bad score or being grayed out. A message could pop up by the comment saying "likely to be downvoted, you are advised to delete this" - and see if more self-policing helps.
Also, if you have some signal that occurs before votes or other comments show up (like a lot of eyeballs on a comment with no upvotes), then maybe you can use that to give users an early signal to delete their comment.