This doesn't fix the philosophical issue, though. Is it the same person? Or did that thread of individual conscious perception disappear forever and was replaced by someone "new" who acts the same?

In the end, this is a philosophical discussion because consciousness is not something we can observe in a way to test and falsify hypotheses.

Hm. The cessation of electrical activity is just that which is measured on scalp EEG; ie, we can only really be certain that the most superficial layers of cortex aren't firing and what we are measuring.

Very fair point. There are other examples that go beyond DHCA, though, and point clearly in the same direction. One example is that sometimes people suffer cardiac arrests and lose consciousness for minutes to hours 10.1016/j.resuscitation.2014.06.015. Coordinated electrical activity stops after a few minutes following cardiac arrest, but people can (rarely) be revived with their apparent memories and personality intact.