2008/10/22 FT2 ft2.wiki@gmail.com:
Unfortunately in most cases, the status of a truth that's non-verifiable, is known as "hearsay".
It's customary in most decisions, whether it be "evidence based research" in science, through to the courts, that a basis of evidence (that independent others can verify) is required, not just hearsay, and the more authoritative the better. Plausibility ("he/she sounds honest") seems to be a lesser standard. To that extent, BLP is mainstream in seeking evidence.
Indeed. Requiring some kind of evidence of claims that contradict a claim which already has evidence to support it seems like common sense to me. Of course, in cases where it's completely implausible for the subject to be lying (how to spell their child's name, say), it might be worth taking a primary source over a secondary source. That primary source needs to be reliable, though - there needs to be a way to make sure they are the person they claim to be. Posting it on their blog, for instance, would be good, posting it on the Wikipedia talk page usually wouldn't.