My partner and I have recently moved from T.O.N.T. to D.O.N.T., and are wondering if some of the latter's bids are useful even if there is interference. For example, if LHO opens the bidding with 1NT, your partner passes and RHO responds 2 clubs, do you still use 2 diamonds to show a distributional hand with at least 4 or 5 diamond pieces + 4 or 5 of a major?
That is something that you must agree with your partner. By default D.O.N.T is off in this situation, but you can agree that it is on. If you use this, it must be alerted. You must also consider how to show hands where the normal bid is impossible. Suppose, for example, your hand is clubs and spades, but the opponent bids diamonds. Obviously 2C is insufficient.