I really doubt that tulpas have much to do with DID, or with anything dangerous for that matter. Based on my admittedly anecdotal experience, a milder version of having them is at least somewhat common among writers and role-players, who say that they're able to talk to the fictional characters they've created. The people in question seem... well, as sane as you get when talking about strongly creative people. An even milder version, where the character you're writing or role-playing just takes a life of their own and acts in a completely unanticipated manner, but one that's consistent with their personality, is even more common, and I've personally experienced it many times. Once the character is well-formed enough, it just feels "wrong" to make them act in some particular manner that goes against their personality, and if you force them to do it anyway you'll feel bad and guilty afterwards.
I would presume that tulpas are nothing but our normal person-emulation circuitry acting somewhat more strongly than usual. You know those situations where you can guess what your friend would say in response to some comment, or when you feel guilty about doing something that somebody important to you would disapprove of? Same principle, quite probably.
This article seems relevant (if someone can find a less terrible pdf, I would appreciate it). Abstract:
...The illusion of independent agency (IIS) occurs when a fictional character is experienced by the person who created it as having independent thoughts, words, and/or actions. Children often report this sort of independence in their descriptions of imaginary companions. This study investigated the extent to which adult writers experience IIA with the characters they create for their works of fiction. Fifty fiction writers were interviewed about the develo
Thus spake Eliezer:
It seems that many here might have outlandish ideas for ways of improving our lives. For instance, a recent post advocated installing really bright lights as a way to boost alertness and productivity. We should not adopt such hacks into our dogma until we're pretty sure they work; however, one way of knowing whether a crazy idea works is to try implementing it, and you may have more ideas than you're planning to implement.
So: please post all such lifehack ideas! Even if you haven't tried them, even if they seem unlikely to work. Post them separately, unless some other way would be more appropriate. If you've tried some idea and it hasn't worked, it would be useful to post that too.