wangus
Be careful to distinguish between an aircraft where MTOW is also the performance-limited weight, and an aircraft where MTOW is not the performance-limited weight, and is simply the structural limit.
At sea level, it's very possible that a full thrust takeoff could be achieved, meeting all the relevant perf requirements, at a weight in excess of the structural MTOW. In that case a derate (or reduced thrust for that matter) takeoff could be used without impacting the TOW, because all your doing is reducing the performance limited TOW, but not below the structural limited MTOW.
The example mutt is giving is for the case where the performance limited weight, at full thrust, is the same as the structural MTOW. In such a case, any reduction in thrust will, in general, result in a lower performance limited weight, and hence a lower allowable TOW. Change the sentence he wrote to say:
based on an example when MTOW can be achieved with full thrust and MTOW -x% can be achieved with derated thrust, so presuming payload is the same, then fuel capacity is reduced so range is reduced.
and this is perhaps closer to what he was trying to say - reduced thrust can mean less range for a case where the reduced thrust means a lower MTOW.
As to the head banging - OBVIOUSLY you woulndt reduce thrust such that your range dropped below the required mission range, as the required tech stop would push up the overall cost of the mission. So you'd only reduce thrust so as to reduce MTOW and hence range for a case where you had excess range at MTOW/max thrust.