Just mentioning the Catholic POV on the original question (I don't have the time to read the whole thread). I'm an engineer not a theologian, I must admit, but I think this is in agreement with Church teaching. Sorry if this is long (or too short).
Much of Catholic teaching centers around God being the only thing that is real, being the Creator. Christ is "the Word," or that original Truth spoken (God's self-image). I've heard of the Holy Spirit described as the love of the Father for the Son (which I suppose would mean that reality and love are the same thing, though I haven't read much into that).
This is what makes "sin" what it is. When one steals, for instance, one denies reality to oneself (in this case, and most cases, several realities: ownership, the relationship between the person and the victim, others negatively affected by the act). Murder, dishonesty, etc. are all made wrong by this reason. So essentially evil doesn't exist. It is the fact that it has no basis in reality that causes real negative affects.
Suicide is an "evil" act. It, like all "sin," denies one's place in the fabric of reality: one's family, friends, responsibilities: relationship with God, others, and oneself.
The Church, pretty much up until fairly recently, would not allow a person who committed suicide to have a Catholic burial. This practice was ended given that a true Mortal Sin (the only kind that would mean Hell, which in context of teaching would mean complete removal from reality: a choice, as well as a punishment) has to be
- a serious matter (check)
- committed with full knowledge of the gravity of the matter (given the probably mental instability: probably not)
- committed with full consent (ditto)
In conclusion: suicide is considered a sin, though the guilt of the committer is probably diminished or extinguished by mental illness.
Also, just because we have a choice in the matter doesn't make all choices or all mindsets in tune with reality.
Steal my dreams and sell them back to me.....