I would propose that no vote would create valid
official policy unless
the vote has been properly sanctioned.
Votes don't create official policy. Official policy is created through
consensus (or less often through declarations by Jimbo, the Board, or the
Arb committee). Surveys are simply something people can point at to say
"see, we have consensus for this".
Having lots of voters, broad application, clarity, a decent voting period, a
static question during the full time of the voting period, and adeqate
public notice are things that can be done to increase acceptance of a poll
as properly reflecting the will of Wikipedians. You may want to mention
some of these things at [[Wikipedia:Survey Guidelines]].
Incidently, VFD polls generally fail at the vast majority of these points.
Sometimes they are clear, and there is somewhat adequate public notice, but
there are rarely many voters, broad application, a decent voting period, and
a static question during the full time of the voting period (the latter
being since the article generally changes during the voting period).
Anthony