This is a specific card effect of 1 single card in the game. There is not some general rule (as mentioned above): "Presence of XYZ character at the site may be such factor [that determines whether a resource is playable at a site]."Konrad Klar wrote: ↑Tue Sep 29, 2020 7:15 am Some other cards/effects may alter playability conditions of a resource printed on the resource's card.
Thanks to Glove of Radagast Noble Hund may be considered playable at non-Border Hold sites. Presence of Radagast at the sites is a factor that determines a playability of Noble Hund.
It's also unclear because you are stating "a factor that determines whether a resource is playable at a site" as if there are multiple factors of "whether a resource is playable at a site," when really, there is only ever 1 factor: being at the appropriate site. This is just one requirement for playing an ally. This is the reason why the original discussion in 2018 was off-base. If anything, the discussion should be on "factors that determine whether a resource is playable at a site".
It's easy to guess that the 2018 discussion would be off-base because people were discussing how allies are played without actually referring to the rules on playing allies.