Or, are you saying that a person should kill himself if and only if doing so would increase his expected utility? I don't think, however, this was implied by khafra's post

That's exactly what I'm saying, and as far as I can tell, exactly what khafra was saying as well.

Whether you will be able to kill yourself in the future doesn't affect the expected utility of that future, except insofar as things which would prevent you from killing yourself would affect its utility.