Whether I agree with that depends on your definition of 'significant' (and 'reliable' as well). Basically, it's just shifting the discussion from relevancy to something that is almost as badly defined. Just like there is a level between "can be seen in one scene of a small movie" and "won an Oscar for best actress" where an actress becomes notable enough, there is a level between "got her name mentioned in two different articles in the Smalltown Weekly" and "had a biography about her published by a mainstream publisher" where her coverage gets 'significant'.
What I see as a major problem in this point is that people tend to have widely diverging opinions on where to draw the line,
Exactly. Significancy is subjective just as notability. The sum of human knowledge includes items that are neither significant nor notable.
As Jimbo says, the criteria for inclusion is verifiability (excluding original research).
Regards,
Ian Tresman www.plasma-universe.com