If you add a comment explaining why you downvoted - and I mean a long-ish comment which goes into a bit of depth to explain the issue you have with the answer - your comment gets rejected, and a dialog box pops up saying:
Don't comment on your downvote. If you think this post can be improved, please offer specific guidance.
That's just wrong, since:
- Downvotes without comments are antagonistic and somewhat hurtful (for posts written in good faith).
- You might well be offering specific guidance in the downvote comments.
- It's much better for the downvoter to leave a sub-optimal comment with some feedback then to be discouraged by this message and not provide any feedback.
Instead, the comment should be accepted (except perhaps for a very brief "-1 wrong"-style comments), and the message could say something like:
When commenting on a downvote, try to explain how this post can be improved, and offer specific guidance.
The comment should remain in edit mode to encourage it to be edited, but canceling the edit would leave the comment as-is (again, except for the case of problematic/very brief comments).
- This question focuses on the specific scenario of a meaningful comment being rejected, and on the rejection message. This is distinct from how to encourage meaningful/positive criticism in general.
- If it's the "-1" indication that is super-bothersome to people, then either this should be removed from the comment (with the rest of it left), or it should be made very clear that is the reason the comment can't be accepted i.e. "don't explicitly mention the downvote in downvote comments" rather than "don't comment on downvotes".