  We congratulate the authors on their exciting paper, which introduces a novel
idea for assessing the estimation bias in causal estimates. Doubly robust
estimators are now part of the standard set of tools in causal inference, but a
typical analysis stops with an estimate and a confidence interval. The authors
give an approach for a unique type of model-checking that allows the user to
check whether the bias is sufficiently small with respect to the standard
error, which is generally required for confidence intervals to be reliable.
