There are a couple of scenarios that might be helpful to consider, as they are examples of mental discontinuity in use today. I cannot convince you of the semantics of "not you" vs "still you", because I think this question is too ambiguous to address satisfactorily.
- general anesthesia is definitely, to some extent a discontinuity of consciousness. You lose time.
- more extremely, Deep hypothermic circulatory arrest actually (temporarily) causes brain death by cooling the body to between 10˚C and 20˚C. All brain activity ceases for the duration of this deep hypothermia.
Are there risks to these practices? Definitely. Some may argue that someone who undergoes general anesthesia isn't the same person. But I would argue that it is, despite the discontinuity, and despite some risk of personality changes.
- general anesthesia is definitely, to some extent a discontinuity of consciousness. You lose time.
- more extremely, Deep hypothermic circulatory arrest actually (temporarily) causes brain death by cooling the body to between 10˚C and 20˚C. All brain activity ceases for the duration of this deep hypothermia.
Are there risks to these practices? Definitely. Some may argue that someone who undergoes general anesthesia isn't the same person. But I would argue that it is, despite the discontinuity, and despite some risk of personality changes.