A crows foot extension will work with a torque wrench accurately only if the wrench is at 90° to the offset of the crows foot. This because the bolt/nut and torque wrench centres then lie in the same plane. Worst case however is if the crows foot extension is in line with the torque wrench arm, increasing the leverage accordingly and so causing over torqueing to that of the wrench setting. Anything in between will also be wrong to some degree.
Edit: posts crossed but we seem to be in agreement, although I wouldn't argue with a crowbar
