I do understand that there is a big difference between an mp3 sourced show and a lossless copy. … but if I received a disc from a trader, I wouldn’t have an idea to detect the difference.
I also understand that traders, who prefer lossless shows and therefore still send & receive shows by snail mail because of the file size, are ready to committ a crime on someone who tries to trade with mp3-shows (intentionally or not). And probably decides not to trade anymore with the sender of such a delight. 
Most of it I understand that it would be ridiculous to turn an mp3 sourced show into wavs to compress them again to shns or flacs… :aliensmile:
…so: how could I find out if it’s worth the effort or not? and how could I protect myself from being murdered because of unintentionally sending mp3’s around?