+1 for undo option. I find undo always better than confirming deletion.
A rule of thumb is basically: Unless you have something important to add don't add anything, otherwise it's just more mediocre comments to sort through. That's why HN has good comments and less noise. Whereas at Reddit and forums and comment systems on other sites, everyone and their grandmother chimes in. Creating a monstrous wall of "thank you"s, "neat", "I agree"s and other babble.