@SimplyBeautifulArt: I'm sorry that they behaved in such a presumptuous manner towards you. Have you flagged their comments?

@SimplyBeautifulArt Yikes. That's not okay. I've dealt with it.

I have raised a flag on math.stackexchange.com/questions/4241410/… for possible plagiarism, etc. I do not have any evidence besides what I have posted in the flag itself, but it seems worth intervention.