HT's stance has always been no to this, because it precludes the possibility of mending fences. I happen to disagree with that, there are people who I simply don't care what they have to say.
If you're being harrassed by someone, .report will allegedly have an effect. I've never been harassed so I don't know personally. I can see how it'd suck though having that first PM in a session from a dolt reminding you to squelch them.
Since HT seemingly won't do permasquelch, .report's about your only recourse.
Wiley.