  We show that bilinear variational estimates of Do, Muscalu, and Thiele
(arXiv:1009.5187) remain valid for a pair of general martingales with respect
to the same filtration. Our result can also be viewed as an off-diagonal
generalization of the Burkholder--Davis--Gundy inequality for martingale rough
paths by Chevyrev and Friz (arXiv:1704.08053).
