The only workable concept of consensus I've ever discovered is
stability. If hundreds of people edit a piece of work in good faith
over a long period, what changes least over time may be presumed to be
there by consensus. However even the most apparently stable elements
of a work may be deposed quite easily. The result may be a new
consensus or, in other cases, a period of instability where the new
version and the old version compete.
As an editing community, I think we're probably far more tolerant of
radical change than we used to be, but probably not tolerant enough.
Most of us (myself included) are somewhat squeamish about junking bad
stuff and starting over, and this squeamishness is probably to the
detriment of the project.
On policy issues, the overriding requirements and purpose of the
project are often ignored or poorly understood by large parts of the
community, which I believe is mostly due to lack of acculturation in
the core values. The antithesis of this is the statement that the
encyclopedia takes precedence over the community. This
encyclopedia-community dichotomy makes consensus-building difficult in
areas of developing policy. However the community quickly falls into
line with new policy once it can be shown to work. In that sense,
policy is what works.