With a vig night 1 kill, we tend to assume TANK-F, but if it doesn't happen till night 2, a later vig claim is more believable.

Plus of course there's the judgement factor, a lot of people who become firmly convinced someone is a DF on day 1 are in orbit, because typically if there was real evidence for it they would have been lynched. Now, a vig would have had a good case to whack Artsapat, for instance, or pretty much any runner up for lynch where the person who got lynched didn't basically prove the runner up innocent. There's certainly cases where a night 1 vig kill is in order, I just tend not to expect better than random from them.

Better for them not to kill, but any of them should ask - especially before a night 1 kill - 'If this person is a town, can I explain my action better than as a hunch to the other townies?'