It’s worth mentioning that this discrimination is sadly necessary. Tor amounts to a massive open proxy, and just about any service that requires accounts (and many that don’t, like IRC or image boards) looks down on open proxies as primary abuse sources.
As someone who has run both an image board and a decent IRC server in the past, it’s a choice between heavily scrutinizing tor connections or banning them outright.
I am impressed. HN does allow throwaway accounts, when necessary to post anonymously. And making that possible via Tor is admirable. There's certainly potential for abuse. I see occasional spam, and angry insults, but nowhere near as much as one might expect. Which suggests either that shadowbanning works well enough, or efficient moderation.
As someone who has run both an image board and a decent IRC server in the past, it’s a choice between heavily scrutinizing tor connections or banning them outright.