Leaving it plugged in has the same effect as removing the battery while it's plugged in (and putting the battery in identical thermal conditions). (Just think: if it were bad, engineering a workaround would be simple.) It's fine to have the battery sit at 100% for short periods of time. The damage you get around the 100% number is from charging/discharging to/from 100%, or leaving it unused for long periods of time.