Although I did see a fairly new account the other day with every comment dead, from the very first one, with no visible mod intervention; I figured it was from being a sockpuppet or someone with a track record.
p.s. I wouldn't want showdead on all the time! I use this "HN ungrey" bookmarklet to see whited-out comments on a page. Also it's useful to read comments that have just been voted down enough to be hard to read:
'Almost invariably'? Dude, I created my first account here a few months ago and was "shadow banned" within 15 comments, simply for expressing honest opinions, which somebody somewhere took anonymous offense to and then SHADOW BANNED ME. Is that fair? Do you expect to attract new faces here with such an attitude? I'm a Slashdot poster going way back, with a mid-6-digit UID there.