Exactly. It's kind of annoying to see that omniscient overlords are censoring people's comments -- but the people being censored get the idea that their comments aren't welcome and then they either shape up or go away. HN has stayed pretty readable as the once-enjoyable Reddit has become the biggest cesspool of stupidity I've ever had the misfortune of reading. (Can you guess by my tone that I used to really love Reddit but it's just not good anymore? It makes me sad.)
So it's probably worth it to delete content that would repel the type of clientele you'd like to attract.