I am not sure if I read about this…but would extra-cellular HBsAg be an antibody sink? Perhaps you read this 2017 paper, where anti-HBsAg antibodies were directed against extracellular HBsAg in mice as an adjunct to vaccination: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4824405/. The role of HBsAg in chronic HBV remains poorly understood, which is why we are having this discussion!