Many people have had bad trips on MDMA. I don't know where this reputation comes from, but it's common to have extremely intense and unpleasant emotions, sensations, or thoughts. Anxiety, agitation, muscle tension, sweating, and/or chills are all documented effects of the drug.
For a dozens of anecdotes, just search "MDMA bad trip".
OK. Firstly, people in academia don’t even talk like this (“what’s your source!”). Secondly, you’re fighting anecdotes with anecdotes, which is fine, except you’re trying to pull the ladder up after you.
You’re coming across as an MDMA fanboy and the way that you’re approaching the conversation will have if anything a negative impact on “the cause”.
MDMA wasn’t ‘designed’ to do anything. It happens to do something. I’m surprised that you’re even phrasing it this way because MDMA fanboys tend to obsess over the lore of its discovery.
I have been present for bad MDMA trips. One of these people has C-PTSD (putting aside the controversy about its existence), and had a C-PTSD-related bad trip, which seems highly highly relevant to this topic.
I’ve done a bunch of MDMA. I’m certainly going to do a bunch more throughout the rest of my life. I’m not going to kid myself about it being perfect. I’m not going to kid myself about the fact that over a large enough population even “improbable” adverse reactions are meaningful. Nerds that do drugs are so often insufferable because they’ll try to intellectualise what’s essentially “God I love drugs and they’re great!”
For a dozens of anecdotes, just search "MDMA bad trip".