Users do have to be logged in to submit articles, so action could be taken against people (or bots) that submitted too many articles that were made dead or did not receive a large number of points.
This is true, but its also true that a lot of times these bots will get to these articles first, and then because they come from a well-known or respected domain, they just get tons of upvotes anyways.
There's two separate problems: too much dead content, which imo, is ok, because the good stuff will usually rise to the top - you need some junk to find the gems; and bots automatically picking up and submitting content - no human discernment as to whether the link is actually HN-worthy. I think the mindlessness is more the issue being addressed here
