“Reliable” and “independent” are two tests, not one. A source can be impeccably reliable and still fail independence, or be independent yet unreliable. Wikipedia asks for both, at length.
Independence means the source has no stake in the subject: not written, commissioned, or supplied by them. A company’s own site, its press releases, and features it placed all fail, however reputable the outlet that ran them.
Reliability means editorial oversight and a reputation for fact-checking: an established newspaper, an academic press, a regulator. A viral post or an open wiki does not qualify, however independent.
The record we look for is coverage that is both, substantial, disinterested, and checkable. Two such sources usually decide a case; a hundred of the other kind do not.
