I'm not sure I agree with Robert Thurman when he writes that it is clear that the Tibetan Book of Natural Liberation "deplores suicide". From what I'm gathering, death is death. Once you enter the processes of the death betweens, how you got there doesn't seem to be much of an issue.

How one navigates the betweens is affected by karma, spiritual guidance, spiritual aptitude, knowledge and practice, and other things. How one died may affect karma (and probably does more often than not), but how suicide affects one's karma may or may not affect one's navigation of the betweens. I'm not reading any indication that how dying from suicide is "deplored" in the between.

And we all know what a conundrum karma is whenever I start talking about it.

The only indication I can find that suicide is frowned upon is through the fact that one presumably does not have a guide or someone to recite to them when they die. And that's not true because if it's medically assisted, you can have someone recite to you. Also there are plenty of ways people die that don't allow for a guide or recitation.

Sorry, Donnie Darko, we do die alone. You can have someone recite to you and try to guide you through the betweens, but it's up to you and your karma to determine whether you can be liberated or you continue in the cycle of life and death. Liberation is hardly a sure thing. And the book itself states that you don't need a guide or a recitation if you can prepare yourself well enough to navigate the between, whatever that means.