Hi, new here as I usually only listen to the audio books. As Siobhan again reminds herself that she is never going to cast through her own flesh this seems like another Chekhov’s gun that she is indeed going to do do it at some point of time. And as I don’t assume she will become an aberrant there must be a “safe” way.
My current idea with little support is this: when you break you only keep the part of personality that was contained in the spell as an aberrant (e.g. Someone casting a calming spell likes the quiet).
If shamans break they keep relatively much, as a lot of their personality is in the spirit world. This is part of why shamanry is restricted by the red guard as much personality leads to complex anomalous effects. Claudio might be a special example that kept especially much knowledge and planning ability, but breaking from one spell is always imperfect.
If you cast through your own flesh you start a long break process that does not consist of a single spell. Therefore each spell you cast etches a new part of your personality and additionally your flesh into reality/magic/the spirit world. Siobhans mom went this path and kept relatively much of her personality even if she didn’t tinker with the spirit world before breaking.
My theory piecing these probably wrong assumptions together is this: if you want to survive casting through your own flesh you need to etch your complete being into reality. This cannot be done in one spell, but must be done piece by piece as any one spell only contains parts of who you are. Siobhans sigil is an important spell at that step as it might be able to bridge gaps. The Naught bloodline also helps as it makes you succumb less quickly from casting through your flesh. So once you cast through your own flesh you are on a race against time and your addiction to cast, choosing the right spells to make yourself stable in reality again.
What do you think? Should I have kept these outlandish ideas for myself? Do you want to add onto or change parts of my theory or do you want to share your own theory?