Thanks for the replies.
I think there could be many "Quranist" agendas, e.g. to gain fame/fortune/popularity/praise, establish one's view, malign certain groups, to unburden themselves of having to follow strict Quranic guidance, integrate or make it more accepting to Western society etc.
In terms of testing this, I think there are a few tell tale signs, e.g....
they do not do what they say i.e. hypocrite, contradictory positions.
when emotionally rattled, or things get tough, or they have to put in significant effort, or use their own money/wealth - their true self comes out
they are not clear/open/honest in the information they present
they will regularly evade/obfuscate, commit logical fallacies in argument - in an effort to avoid being exposed/refuted
say one thing in public and another in private
"if you want to test a man's true character, give him power."
-- Abe Lincoln
I like this saying. It reminds me of this post: http://free-minds.org/forum/index.php?topic=8609.msg26554#msg26554
When someone is in a position of power, to do with you as they please, then it is indeed a test of character if they remain true/just/righteous/etc when dealing with you, even if against their own kin etc, as per Quran, e.g. 4:135.
Something to think about.