AbigailII: Okay. Let me answer your points as directly as I can:

[For the last time. But you don't seem to be able to grasp the concept that rules should be complete, and not refering to things that aren't defined.]

I fully accept that the rules should be complete. I fully accept that the rules should be correctly implemented. There should be no ambiguity and there should be no bugs. Similarly people should always be fair and the sun should always shine when we want it to. In other words it doesn't matter what should be, it matters what is. And I am only arguing about what is - the bug and the (English) rules as written. The grey area is in what these things mean and that's what this debate is about.

So:

1) [The rules of backgammon (as stated on THIS site, not rules of backgammon defined by some other identity)]

I am talking about the rules on THIS site and no other.

2) [.. nowhere state that if it is possible to move with both die, you have to do so. (This is your MDU rule).]

There IS an MDU rule - it's the one that the Fencer-acknowledged bug fails to enforce.

3) [Considering that you have to pass if there is no legal move available (no my words - read the rules), and you call this situation "impossible moves", it seems that what you call "impossible moves" is what the rules call "no legal moves".]

The rules say that the player "must pass" if they "cannot make a legal move". The use of the word "legal" in that sentence is irrelevant. It could simply say "cannot make a move" and it would still be correct. There would be no change to the meaning, either literally or by implication.

Here's a choice for you:

3a) There is a distinction between possible and legal. It's impossible to move past a prime. Legality doesn't come into it. It's impossible to come off the bar into a closed table. It's true that there are no legal moves but that's because there are no possible moves. The impossibility of a move precludes legality; you cannot judge the legality of a non-move.

Or let's say that you can't bring yourself to agree with 3a).

3b) All impossible moves are in the illegal moves category. It should be obvious that there are possible moves which are also illegal. Illegality would then be a concept that applies to all impossible moves and some possible moves. These last constitute two separate sets.

4) [Again, the rules do not define any MDU rule.]

Correct, the rules do not explicitly define an MDU rule. We have agreed on this several times now. ;-p

5) [Therefore, the "no swapping possible if there's no legal move for the second die" isn't referring to the MDU rule, because there is NO MDU rule.]

It's quite the opposite, I would suggest. This no 'Swap dice' link shown when there's no legal move with the second die" covers two situations which I've shown are separate (see 3a) or 3b), whichever you prefer).

5a) The first is when swapping the dice makes no sense because using that dice value is impossible.

5b) The second is when swapping the dice would lead to a possible but illegal move.

6) The obvious question is "what are these classes of possible but illegal moves?". The non-MDU-compliant moves are the only known class so far. And I invite you, yet again, to come up with another because my argument will collapse if you do. Go for it! ;-)

7) The sentence must therefore imply the MDU rule.

Conclusion:

The MDU rule is a BrainKing rule that is both implied by the written rules and acknowledged as a behaviour that the backgammon server should enforce but doesn't. Non-MDU-compliant moves are therefore against the rules, illegal, not to be done, yada, yada, yada.


Let's try a different tack.

Q: Does the MDU bug exist?
A: Without a doubt. It's clearly documented in the bug tracker (and, besides, it's what triggered these debates!).

Q: Is the bug really about the MDU rule?
A: Absolutely. Both of the original instances in the bug tracker as well as Wil's new example are cases of MDU rule.

Q: If this bug is a failure to enforce the MDU rule, doesn't that mean that the MDU rule is part of the BrainKing rules?
A: As Spock would say: "Logic dictates this".

Q: But if the rule isn't explicitly stated on the rules page, doesn't that mean the rule doesn't exist?
A: No. As the previous question indicates, the existence of the bug implies the existence of the rule. It should be assumed that the written rules are lagging behind and need updating.

Q: Ah, but if the rule isn't written and there's a bug which means the rule isn't actually enforced, then surely there is NO MDU rule.
A: You can certainly argue that point but it doesn't negate the fact that the bug and the written rules imply the MDU rule.

Q: Implied? Only implied?? That's not strong enough for me!
A: Ain't nuthin' I can do 'bout that!

LOLOL.