@Last-Don-Pablo Believe me, most of the people in this thread are not locked into a "tolerance" explanation. We have noticed the same things you have: that new users do not roll; that old users roll fine on some products and not on others; that come-downs on the "meh" product are different or non-existent. It seems like a different compound. We have all noticed that.
However, I also want to be open minded. I have tried many different products since I started participating in this thread years ago. None of them have been like the stuff I had in the 00s. I am willing to consider the possibility that the problem is something with me. However, I am also willing to consider that the problem is the product.
I agree with almost all of your observations, and have stated the same things previously. I have also noticed that on the "meh" product I get very agitated and can be mean. I was at my favorite band's performance on the front row, and all I could do was feel pissed at a guy next to me who was being loud. I could have fought him, I was so mad. This was on 200 mg of the "meh" product.
I have also observed at least two people who had never done MDMA on the "meh" product. They were unimpressed and obviously not "rolling face" as you said. One of them actually shrugged her shoulders and said it was "ok." The other girl talked about a lot of negative and depressing topics. Compared to new users I watched in the early 00s...totally different. There used to be physically observable phenomenon: dilated eyes, askew jaw, wide eyes, eyes rolling back, rubbing/touching self/others. I did not see any of that with these newbies. However, I did attend an event and saw those behaviors from some people in the audience, so it seems that the product I am familiar with is out there for a minority of individuals.
In any case...
I made a post awhile back that summarized our top theories. However, it is super hard to find posts in this 177 page thread. So, I will summarize again.
Current working thesis statement:
Variations in MDMA synthesis methods result in variations of product due to either a) presence of active impurities or b) substitution of structurally similar compounds.
There are multiple published research articles that indicate that synthesis methods result in different impurities. There is also a published research article that shows that some seized product that appears to be MDMA is actually a different but structurally similar compound that fools GCMS testing. There is also published research that shows that at least some impurities interfere with the effects of MDMA.
We have a few efforts underway to try to prove any of this. I have been in communication with DrugsData (formerly ecstasydata), and they are looking into the "structurally similar" compound theory.
@vash445 is also running some tests with the help of someone he knows. We are hoping to come to some concrete conclusions.