while the word 'dirty' can certainly be used to describe pills which are mdma + XXX and they may make you feel weird in the head, have difficultly constructing sentences, diff walking, etc. In my experience with pill reports is that everyone likes to give the pill they had a good score. So if you see something which reads like "8/10 - A nice CLEAN dose of mdma, smooth, no real comedown, very chatty, lasted a few hours, no eye wobbles, etc" you need to interperet this as "3/10 - Really weak dose of mdma, at least i felt ok the next day, since i didn't really get the experience i payed for, what a bloody waste of 40bucks, i wish I had a good contact to get pills which actually work. At least it was mdma."
While you may also see this "8/10 - strong dose of mdma, DIRTY pill, Lots of eye wobbles, jaw clenches, fucked vision, loved up, 'smacky feeling', nasty comedown and headach next day"
That could either mean "9/10 - Fucken big dose of mdma, clasic mdma experience, recommended"
or maybe "8/10 - big dose of mdmda, however, possible mixed with speed, K, etc. Either way, Very Strong pill, recommended."
Just my 2cents