Thanks for this post. It is thought (& memory) provoking.
I don't think of SI as punishment, sometimes it is even a self-soothing behavior (like knowing I have an option, and sometimes, yes, I do think of it as something that is just something that should be...)
But, when I first had the thoughts as a teen, I remember now, they followed anger and a sense of not being taken at all seriously, of my pain being dismissed and I remember two ways of thinking, one was "they will know I am someone to take seriously...", the other was "I just can't stand feeling this way..."
I never thought of it to punish me so much as, sometimes (when my kids were very young for instance...or before that in my marriage...) setting others free of me. (with the exception of my parents I guess who I thought of "proving" something to in a twisted way, I suppose a way to punish Them for the way they dismissed my feelings)
Now, alone, I find myself thinking either that I can't stand the pain, or that I won't be able to do the few things I still want to do and so...why stay...why not choose instead of being left to who-knows-what ending... But, I know it would do damage to the grown children I care about in one way or another and I can't bear to hurt them that way---I have seen how losing two uncles to suicide has affected them. ((and then, if the pain is great, I turn to the thought of accidents...no one need know...))
(when my brother killed himself, I know it was out of terrible pain and anger at himself, some others thought it was to punish someone else, but I know better....it would have been better had he been a drinker to go out and get drunk, or had he been able to self-soothe...somehow...when it is someone else, I never think it should just be...)
I don't want to punish but to release myself, or others of my potential burden.