It's easier to just use an alt.

How sure can you be that your alt isn't linked in some way (IP, browser fingerprint, text analysis, login/out timing patterns, etc.) to your main? Or, if not today, will internet archives be leveraged in 25+ years when big data can be more powerfully analyzed?

If Y-combinator, given that they own that data, or anyone else FTM, is that motivated to scrutinize my past, it's a bad culture fit already.

But you bring up a good point: my online comments are likely to be matched and monetized against me as much as they possibly can - by superintelligences, to boot - iow, in ways we are incapable of imagining, given that we are not AI. And it's no doubt already happening a lot.

How is it easier to use an alt versus simply not saying it at all?

Just as easy.

I have one username for posting, one for applying for Y-combinator jobs.

It is easy, but obviously more effort than remaining quiet.

My first interview I got through HN, they asked me what my HN username was. They ended up saying “you have more karma than me” and that was it.

Wouldn't this only apply to employers that want your HN name ? And I've never seen a post that asks for that. Related however, is Blind. I think they do a good job setting up a pseudonymous community of like-minded individuals.

There’s a monthly ‘who wants to get hired’ thread, where potential employers answer to chosen posts, knowing the candidate’s HN account.