ALL drugs harm your liver. Your liver removes toxins from the blood. The latter part of your question is the one I probably can't give you a satisfying answer for. Alcoholics abuse alcohol EVERY DAY! That's why their livers can get pretty fucked. Your liver is meant to remove toxins, even if they are slightly damaging, it'll quickly recover. The problem becomes over working it day after day. This does not happen when using e in STRICT moderation. Where does MDMA harm the most for the longest, even after one dose? The brain stem by far. I wouldn't worry yourself to much about any other body parts.