Actual coma's involve such a low level of consciousness that often a lot of time passes without much going on experientially, even dreaming may be limited or memorizing dream-like states does not happen very optimally.
I've been through what szuko describes multiple times: the death-rebirth cycle experience. While experience can be compressed temporally, I think it's misleading to compare the experience to actual countless lives being lived but it is rather the feeling of dying and being reborn: high level of consciousness slipping in and out of coherence (with the slipping out often being into a white-out rather than a black-out which is in many ways the opposite), rather than dropping off at the low level.
I recommend this big think talk, among other things about the thalamus:
http://bigthink.com/videos/andrew-newberg-neural-enlightenment-101
Mystical states or such that was described do tend a person more experienced since the experiences are very intense and leave a strong impression, they can also shift a person's views the more compelling they are. Relativity can be forced on a person's paradigm.
I think the point is that a coma is not a risk of psychedelic tripping, but time dilation or mystical states can make sure that an experience lasting only hours in real-time can have the impact of something typically much grander - it that sense it can change a person quickly or acutely, and compared to real-time it is at a high rate and can be called catalyzed.
The wisdom comes from the inevitable confrontations in life that are universal. Even though they are subjective and experiential they are so universal that it can be shared and utilized and usually affects your world view, but it opens you up to truths which can definitely ruin ignorance of youth.
Wisdom is not even yet realization let alone actualization, so often people can intuitively develop themselves but not necessarily live or act completely according to their new-found insight. In my experience this can be very frustrating and can be like premature development. The more you get ahead of yourself out of sync with your life, the more questions may be raised and the more difficult it could be. I think a person going through enough of such experience soon enough could pretty much go through a mid-life crisis at a young age.
It's not good or bad, but it's premature if you are not middle aged.
To answer your question directly: I have never heard of people going into a coma from psychedelic OD. Different things happen from that, there is a physical component for those psychedelics that have a narrower therapeutic index, and blood flow in limbs can become a problem for some (as an example). Mentally szuko covered a lot: a person can flip out behaviorally or have a very heavy experience with large impact mentally. Very altered states of consciousness can have very atypical effects on people, I'd say it can change them but unpredictibly.