every day I learn bot comments on ao3 are stooping lower and lower
anyway if you get a comment like this, chances are that they are bot and their goal is to do whatever it takes to get you to delete your work, most certainly (from what I’ve heard) it’s because they want to “safely” steal your work, use it to train their ai without you being able to rightfully claim ownership of your work since “there’s no proof that the work was stolen/was posted elsewhere first by you” because the original source has already been deleted.
report their comments to ao3 for spam—in this case, specifically, I think you may be able to report them for harassment too—and don’t pay attention to them, most importantly don’t delete your works, don’t feel discouraged by their comments. remember that they are bots and they mass comment something like this on people’s works at random to get people to delete their works. (or even if they’re not bot, they are still pathetic bullies who don’t deserve your time or attention.)
MORE ABOUT BOTS AND SCAMS PLAGUING AO3’S COMMENTS SECTION HERE