  We provide a unified approach to a priori estimates for supersolutions of
BSDEs in general filtrations, which may not be quasi left-continuous. Unlike
the previous related approaches in simpler settings, our results do not only
rely on a simple application of It\^o's formula and classical estimates, but
use crucially appropriate generalizations of deep estimates for
supermartingales obtained by Meyer. As an example of application, we prove that
reflected BSDEs are well-posed in a general framework which has not been
covered so far in the existing literature.
