While I agree that a dominant should be as observant as possible to avoid problems, I think that a sub also has an obligation to be honest about limits. Any sub that would violate their limits in an effort to please a dominant is missing the point.
Honesty is essential if the relationship is to succeed. While a dominant, by the virtue of being in control, is responsible for the scene and aftercare. It is too much to also be asked to read a subs mind.

Barton