The per se rule on defamation is on Reddit not here. That is because defamation isn't harassment in reality. Worse, he can't defame your internet pseudonym. You could argue that as a brand it's experiencing defamation, but you'd have to prove specific damages to your income using AbleistSL as your brand. And this is all just for it to be actionable as defamation. None of it would be harassment.
I suggest you just ban u/CatoTheElder because the cunt is committing actionable defamation, which is legally criminal harassment.
The per se rule on defamation is on Reddit not here. That is because defamation isn't harassment in reality. Worse, he can't defame your internet pseudonym. You could argue that as a brand it's experiencing defamation, but you'd have to prove specific damages to your income using AbleistSL as your brand. And this is all just for it to be actionable as defamation. None of it would be harassment.