I know of no exception.  In fact I believe you would need to use coercion in order to attain it.  Similar to how the dollar is maintained as a standard. 

That is one of the more interesting things about BitShares.  It doesn't pretend that math can save you if you don't have a consensus in meat space.  ie the meatspace consensus requirement is not ignored as in most other cryptos, but is actively encouraged.  I often wish that it could be based more on math, and hard results, but such is the nature of my fellow man.  I am glad to be part of a community that doesn't hide from it.  Even if I don't always agree with them.