> most people DGAF about random HNers

It is never most people you need to worry about.

> if someone needs to use throwaways to post negatively polarized statements on HN

If it were only read by other HN users who understand that a user account is not a human then it wouldn't matter, but the world is not so simple. There are people, who do not understand that forum accounts are not humans, who are working hard to associate internet activity with humans and will use it against them.

Of course, we already know how to identify individuals by their writing style, so a throwaway account probably isn't the screen the OP hopes it is. Still, it is the best source of making it as difficult as possible we seemingly have.