  The superconducting state and mechanism are among the least understood
phenomena in twisted graphene systems. For instance, recent tunneling
experiments indicate a transition between nodal and gapped pairing with
electron filling, which is not naturally understood within current theory. We
demonstrate that the coexistence of superconductivity and flavor polarization
leads to pairing channels that are guaranteed by symmetry to be entirely
band-off-diagonal, with a variety of unusual consequences: most notably, the
pairing invariant under all symmetries can have protected nodal lines or be
fully gapped, depending on parameters, and the band-off-diagonal chiral d-wave
state exhibits transitions between gapped and nodal regions upon varying the
chemical potential. We demonstrate that nodal band-off-diagonal pairing can be
the leading state when only phonons are considered, and is also uniquely
favored by fluctuations of a time-reversal-symmetric intervalley-coherent order
motivated by recent experiments. Consequently, band-off-diagonal
superconductivity allows for the reconciliation of several key experimental
observations in graphene moir\'e systems.
