I have unfortunately gotten into a shouting match with another MSE user on the question referenced below. I would like to flag the user's latest (slanderous) comment to my answer but I see no option to do so. Maybe I have not enough reputation? What then can I do? No, I am not interested in retaliatory diwnvotes which cost me reputation and do not really solve the problem.
Comments are ephemeral. Don't let a misguided comment get you down. If a negative comment is valid, you might improve your answer in response. If a negative comment is invalid, either ignore it or explain calmly why it is not true. Don't fuel a flame war.
If a comment is rude or offensive, flag it as such.