I don't know if you're saying that you do or not, but as far as anecdote goes: yes, lots of people do. I don't really care, and my points get to stand on their own merit.

Why would anyone do that?

I don't, but the primary reasons to use a throwaway account are if you want to discuss something deeply personal without giving yourself away, or hide your identity so you can BS or insult people. It's easy enough to be anonymous on HN and still have a persistent identity; if someone resorts to burner accounts others are going to assume it's for trolling.

I've had this account for more than 3 years as you can see. I can't help if people incorrectly assume it's a burner because of the name. I considered it throwaway at first, but I don't care to bother to change it at this point. And like I said, it lets my points stand on their own merit, which I consider a positive.

I have to admit I don't bother to pay much attention to the exact handles on throwaway accounts.