I understand the purpose of washing MDMA is to get out all of the impurities. But what's the purpose of recrystalizing it? If you've already washed MDMA with acetone hasn't that already removed all of the impurities? Also how would you make sure there is no acetone left on the MDMA crystals after washing?
Recrystalization is done almost exclusively for resellers. A lot of people want their mdma in nice big rocks or crystals, not powder or sand. It has no bearing on the purity of MDMA.