I think that's too broad an interpretation; based on the example in the clarification, I think it was intended to say that if you discard a card to pay the costs of the action, you can't play the card you just discarded as the effect of that action.
So if one of the cards you discard from the top of your draw deck for
BtM is, say
Gimli's Battle Axe, you can't use it to play that copy of
Gimli's Battle Axe. This is all that that rule is intended to prevent.
As long as you're not playing a
weapon as part of the effect of
BtM, the rule about actions playing cards from your discard pile doesn't apply because you're not actually playing a card from your discard pile.