This suddenly has me wondering if TR-Feast should lock in on gaining the same card twice.
It definitely shouldn't. The only reason a Throned BoM has to be the same card both times is because BoM effectively becomes that card once it's played. If you resolve the full text on Feast twice then there's no reason why it should have to be the same card you gain.
It's a thought exercise, really.
TR locks in on the played action. In BoM's case it is: TR-BoM(as CardX) meaning the next time you play it, you get BoM(as CardX) which is why there is confusion about which tokens you get.
TR-CardX(+1 Buy) = CardX(+1 Buy) + CardX(+1 Buy)
TR-BoM(as CardX(+1 Buy)) = BoM(as CardX(+1 Buy)) + BoM(as CardX(+1 Buy))
TR-BoM(+1 Action)(as CardX(+1 Buy)) = BoM(+1 Action)(as CardX(+1 Buy)) + BoM(as CardX(+1 Buy))
It just seems counter-intuitive that you lose the BoM token on Throning. It can still lock in as that action card (i.e. BoM(as Feast)) because the action you chose was BoM(as Feast) to play twice.
If you Throne BoM as Feast, you get BoM(as Feast) + BoM(as Feast)
If your BoM has the +1 Action token, and you play it as Feast, you get BoM(+1 Action)(as Feast)
If you Throne your BoM(+1 Action) as Feast, why wouldn't it become BoM(+1 Action)(as Feast) + BoM(+1 Action)(as Feast) ?
This does not violate what Throne does, or what Band does.
I don't see what this has to do with TR-Feast locking in on gaining the same card. BoM literally becomes the copied card (well, "literally" in the context of the game), so it has to be the same on the second play off of TR. It's the only card in the game that works that way. Throne Room doesn't double the effect of playing a card once, it just plays the card twice.
As for this interpretation of the TR-BoM w/ tokens issue, I think it's feasible, but I still don't think it makes the most sense. As I understand the wording on BoM, it sounds like you never actually "play" BoM. You just play the card it's copying. That interpretation is kind of unfortunate in that it would mean putting tokens on BoM is completely worthless (maybe barring a few edge cases, but I don't actually think so), but I also think it makes the most sense. There are a handful of other interpretations that I think could be justified (get the tokens on both piles twice, get the tokens on both piles once, get the tokens on BoM twice, and get the tokens on the copied pile twice could all potentially make sense depending on the precise meaning of the wording on BoM, I think), but I just don't understand the rationale behind getting the BoM tokens once and the copied pile's tokens twice.
For clarity (if anyone wants it), here are the reasons I think those 4 interpretations could be justified:
Tokens on both piles twice: BoM is a card from the BoM pile and an honorary card from the copied pile. Therefore, it gets both tokens on both plays.
Tokens on both piles once: It is BoM on the first play, becomes the copied card halfway through resolving it, and is the copied card on the second play.
Tokens on BoM twice: BoM, as a physical card, is from the BoM pile, so it only gets those tokens.
Tokens on copied pile twice: BoM, for all intents and purposes, becomes the copied card the instant you play it. It is no longer BoM at this point, so it only gets the tokens on the copied pile.