I have a few comments to add:
I live near to the south pole.. country un-named as there are to few people here. In the past 10 years I have seen the quailty of 'mdma' or rather mda decrease, maybe this is partially my fault, maybe not..
Pills were good, 10/10 everytime here and readily availible. Reseach Chemicals unknown back 'in the day'. I pioneered RC's in this country, yes, mainly to make a buck. I put my body, mind and soul through hell trying to find a mixture of chemicals which had a relation to the proper mdma as I knew it back them, nothing compared, nothing ever will.
I spent many many nights trying psyco mixtures, which, at a dose rate cost less than 3 dollars. I gave up, yes, I gave up after a seriously bad trip.. It wasn't me.. I stopped drugs alltogether infact. Pills were worth 50 dollars at the time..
I came back after 3 years with a degree under my belt (pills worth $30) and gave a pill a shot... It was littered with RC and I hated it. Tried several more and had similar effects... I would guess now that 9/10 pills are packed with that shit here, I actually refuse to take them now.
I think it might take a person with experience to pick up on it, newbies have no idea...