Your point is well taken, but ephemeral nyms aren't new. I actually like knowing they are out there. You need to evaluate what you read on its own merits. And there's an aspect of rebelling against the logic of accumulation.
I don’t have unlimited time to read comments so I prioritize ones from the patio11, cperciva, and ChuckMcMs of the board. Not because who they are IRL but because a history of posts I found interesting, informative, etc. makes it more likely the next one will be too.
If you are on a throwaway because you want to talk about being a functional alcoholic without your colleagues knowing: https://news.ycombinator.com/item?id=27363003
that’s perfectly reasonable. But if you are on a throwaway because you want to attack the concept of reputation, that’s a pretty negative signal.