Hmmm, the few negative commenters I've had, I've eventually switched them into fans. Maybe it's the way their comments don't phase me, we end up having good conversations with one another, they start liking me as a person, and following my comic as a way to hang out? Maybe? lol idk
Basically, I roll with the punches. If I were to get something that was pure venomous hate (I never have yet), I'd delete the comment and carry on unphase. Little jabs and pokes at art/writing are easy enough to make a small joke back, maybe a silly pun, and carry on.
Main thing is to not let it get to you. Our comics can't appeal to everyone and that's ok, there are plenty of other people out their that'll appreciate what you're posting. Also there are a lot of people online that talk in sarcasm, and by not taking each comment personally you run less of a risk in misinterpreting a sarcastic poke for a negative comment.
One time at a convention, I had a father and his about 8-9 yr old son come up to the table. His son loved the look of our comic and wanted to buy an issue. The father read the first page and asked, "This character's name is Plague? How am I suppose to explain what that means to my son?"
lol He didn't buy the book that day, they left and next year we crossed paths again at the same convention. The son still wanted our book, and the father read another page and asked the now about 9-10 yr old son, "Heirloom? Do you even know what that word means?" The son sheepishly said, "No..." then the father asked me again, "How am I suppose to explain this to my son?" I answered, this time, enthusiastically, "It'll give you a wonderful opportunity to spend some time with him, learning something new." The son looked up excitedly, and the father bought our graphic novel.
My pro tip: Be kind. Be positive. Be thoughtful. And don't let things bug you.