I don't like the mob thing either but it's how large group dynamics on the internet work (by default). We try to mitigate it where we can but there's not a lot of knowledge about how to do that.
To explain a bit more:
On the one hand, you need a critical mass of people to have a discussion. On the other hand, large group dynamics seem to be a problem.
HN is generally many multiples larger than the critical mass for the former, at least on the front page. Attention drops off a lot if you go further.
So as an experiment, you could do something like 'rendezvous hashing' to show each user a random 10% subset of submissions. (If you want to gradually introduce it, run the experiment on 20% of the users only, but show them a 50% subset, so that each of the longer tail items still gets 10% of total users? You can play with the numbers.)
You could make this opt-out, too, so that people don't create ten accounts in the hope of seeing everything. Direct links would also still work.