You can use a longer-established /hn/account to vouch your burner's posts... unless you're worried about /hn/ linking your accounts, too (not just public scraping) — which they can, by IP address.
In the current system people can vouch for dead posts from shadowbanned new accounts, if I understand correctly. It seems people do it, to a certain degree at least, because I rarely see good comments that stay dead forever.