HI.
All I know is that when I used to work in a 24hr Crisis Home for Sexual Abuse Survivors, was that many of the clients came from horrible backgrounds, including Ritual Abuse, and many of them would have MUlti Personality Disorder and do things they actually believed they had to.
In other words their Alters would take over.
For some it was all that they felt good enough for they did not believe that they had anyother positive qualities in life. A lot of them just turned to what was most familiar to them, and stated it was a way to take back some control (IE They were the ones who decided when and where this stuff would happen, not having to wait for the unexpected)
Some of the clients unfortunatially went bak to their oler ways, but most of them with lots of support and guiedence were able to cange how they lived their lives and were able o stop , also with intense therapy the DID clients were able to become their own self again and not have anymore alters.

Look at me I'm one to talk, I self harm sometimes, but never to the extent that the people I've ever seen and also heard of as you mentioned.

The only reason I don't work there anymore is tat another bigger agency took over as we were a small orginazition, and I was layed off.
Hope this helps you to understand a little.
I deffinatly believe that it is subconscious and a big cry for help.