Currently if you curve a grade it cannot be undone. Some instructors are new to curves and may not understand or be able to predict what the Canvas redistribution on a curve will do to the scores.
Two possible solutions:
1. provide a preview of scores and a button to accept or finalize. Seems standard procedure for important changes in most software.
2. provide an UNDO for the curve- another standard option.
Also, we should have more than one method to curve available for different situations; see Curve grades based on square root