As I see it, HN is about the conversation. I don't care who brings up a topic, if it's interesting. And then, I'd prefer to see discussion focused on that one submission thread, instead of spread across 3 or 5 or more follow-on submissions, particularly those placing #, ?, etc. at the end of the URL.
If posting does not bring karma, maybe this would help reduce the number of threads and increase their concentration of ensuing conversation.
I'm not sure, though. Something subconscious tells me I'm not seeing the other side(s) of such a change.
Also, if possible, I think the duplicate checker would benefit from being enhanced to detect at least the more obvious/prevalent workarounds, e.g. those same #, ?, etc. Of course, this, of itself, likely leads to an arms race. But maybe it would have at least some temporary value.