Why is this even an arguement? The guy evidently has a problem with the "goop". BIG DEAL. If you dont want your amp with goop in it, dont buy one. It's NOT however gonna change the value of the amp depending on WHO modded it. Marks amp will definetely NOT lose value, plain and simple. And while their are planty of "other" modders out there, NONE of them sound like Marks amps do, hence the price tag on them. Sure they sound great, but in different ways.
deal with it, it's not that big of a deal, if you dont like it, dont buy it. Why argue with someone who doesnt care about "goop" and cares about TONE.