I would argue (and have before) that the hands where I would not be interested in knowing what an Alerted overcall of 1NT was for *any possible Alertable meaning* - even *any Alertable meaning that is currently not extinct* are such that *failure to ask* would be passing more UI than asking. I'm not in the EBU, but I *always* ask about overcalls to NT (partly because we play a weak NT in a strong NT world, but mostly because it's always different. Yes, I know that I'm keeping them on the same page. Oh well.)
Note, this is not a universal rule. But (1NT)-2
♦!, without thinking hard (as in, I've played all of them myself), could be:
- diamonds and a higher suit
- hearts
- spades
- spades and another
- both majors
- either major
- three-suited including diamonds
- three-suited including spades
What "unusual interest" does asking opposite 15-17 show? That I might make a call if they have a 11-14 hand, or an aggressive intrusion hand, or one or both majors, or diamonds, or not diamonds? Sounds like any hand with more than a 5 count, and many hands with fewer but a long suit.
Different, of course, is when it's a more one-expected-meaning Alertable bid; different yet when it's an unAlerted bid; different yet when it's the "What does 3
♦ mean?" "It means you want your partner to lead diamonds against NT" or "how many hearts does 1
♥ show?" "Fewer than you have, obviously".
When I go to sea, don't fear for me, Fear For The Storm -- Birdie and the Swansong (tSCoSI)