Zero evidence for this, as far as I know. The idea that it could actually undo neurological damage seems even more remote.
I'm not completely dismissing the idea, it is just very, very risky and is based on anecdotal evidence from people on the internet. When I took drugs, post hppd, I would sometimes get an afterglow for a while, then crash even further down. Maybe they posted their anecdote during one of the afterglow periods.