One thing that pseudonymity will do is allow you support positions you don't actually hold. To steel man them. To really stretch your brain to find the best way to present and argue in favor of them. Doing so pseudonymously means never having to explain yourself to friends, family, employers, or three-letter organizations later.
This also works really well for positions you're leaning toward but don't know why. Or half-baked ideas you'd like someone to respond to. Or just questions that you're embarrassed to ask.
This may not fit with the letter of the HN guidelines, depending on the distinctions between "throwaway," "pseudonym," and "temporary pseudonym":
> Throwaway accounts are ok for sensitive information, but please don't create accounts routinely. HN is a community—users should have an identity that others can relate to.
https://news.ycombinator.com/newsguidelines.html
But I think it fits with the spirit. From "What to Post?":
> On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity.