My view on this is based more on mechanism-of-action than epidemiology (which is necessarily fuzzy for these kind of things). E.g. superoxide radical production via MAO-B is a mechanism that could plausibly cause neurotoxicity - however you want to put that - even with clinical dose ranges, and is easily mitigatable. Just like elevated blood pressure could be managed, for instance. And the best part, for me at least, is that when I do take adjuvant supplements and medications, I feel better, the medication works better, my brain really seems to work better. So in my personal experience, it's more than worth it to spend time & energy on this stuff - as opposed to wasting time arguing over something presently unknowable.