[steinhol]

After partner's bid RHO asks "Is that forcing?" or "Do you have to bid?". Surely not entitled to a Yes or No. Explanation could be "partner is expecting a response, but no requirement". This arose - LHO opens 1D, double from partner - first time we had played together, so no agreement, but fairly standard. Surely if RHO passes I cannot be required to bid?

[Cyberyeti]

This is a simple no, you can easily have 6 good diamonds and wish to convert to penalties. If you want to be more generous, "it's takeout, but I can pass with a lot of diamonds".

[mycroft]

"I am expected to bid, yes".

or, if you're feeling generous, "it's takeout, but of course I am allowed to convert".

There was a thread years ago where someone claimed opposite something like 1NT-DONT double (one-suited hand), they'd ask the bidder to leave the table, and then ask responder if double was forcing, and base their decision on the answer. Now there are even more reasons that that is wrong than the OP, but my response was "I look forward to the day this happens and I have a decent 15. Because I'm going to say yes, and then I'm going to pass. And when he complains about that, the response is 'but I had a penalty double'."

In a similar thread (this one over 1NT(weak)-X-p forces XX) I saw a response (from Cyberyeti, in fact) like "it was until you asked that question". Again, not exactly the right thing to say, but gets the point across.

In answer to your "Surely not entitled" - they are entitled to your agreements. If your agreements are "we never pass this", or even "we never pass this unless we psyched" (1NT-2♣ Stayman, for instance), then they are absolutely entitled to "yes". Of course, as always in bridge, " 'always' means 'almost always', 'never' means 'unless you're sure it's right'."

In many cases, people that ask that question are fishing to find out if they can pass with a bad hand and no diamonds, because you won't sit for it. They probably don't even know they're doing it. So "it's a takeout double" seems like the correct explanation. If you decide to pass with 10 high and ♦KT98xx, then you get the blame if it makes.

If they push for a "yes" or "no" after that, call the TD, especially face-to-face. The UI transmitted by the questions to opener is quite high, and you want the TD aware in case there's a potential use of UI call later. Even if opener doesn't hear the questions, the TD can let you know how detailed your response has to be.

As a TD, if I determined that responder really did want an actionable promise that 1♦X would be pulled, I'd quote Law 40A3 to them. There is never an actionable promise about any future call.

Very sidetrack in spoiler:

Spoiler

I play Power Doubles in this auction with one partner, and we Alert our passes (as well as our doubles of course), specifically because expected trump strength is more like ♦QT95 than ♦KT9xxx. It's important to declarer to know this is more a "power pass" than a "trump stack" pass in the play. The "obvious" meaning of a "convert to penalty" pass is that, well, obvious.

[barmar]

Players are allowed to violate agreements, so long as they don't do so enough that a different implicit agreement is formed. So even if a bid is forcing, the opponents may have little redress if the player chooses to pass it.

[blackshoe]

Tell 'em your agreement. Then do what you want. If they get upset, tell 'em to go see the Chaplain.

Comment made by one of my roommate's "deck apes" in my first ship, after Wally sent the guy to get counseling from the Chaplain: "Mr. Purio, I'll do anything you want, just don't send me to see the Chaplain again!"