The anthropic trilemma is a question that wouldn't be raised unless the questioner implicitly believed in souls. The attempt here is to make people realize what it really means to have a reductionist view of consciousness and subjective experience.

I'm not sure what you're referring to by "souls" there. Right now I have this subjective experience of being a consciousness that is moving through time. I anticipate a sensation of "moving" through new situations as time goes on, and things like the anthropic trilemma refer to my expectation of where I will feel like I end up next moment. I think we agree that our minds have no objective property that follows them through time, at least no more than non-conscious objects. But there does seem to be some subjective sense of this movement, leading to a big question: If we don't have souls, why does it feel so very much like we do?

I'm mostly content to say, "Eventually neuroscientists will piece apart enough mental processes that we can describe the neural activity that causes this sensation to arrive". I also classify this sense of a "soul" in the same as something like the colour red. Why does red look like red? I don't know. I intend to eventually find out, but I'm not sure where to start yet.

If you really want the thread metaphor, then imagine a thread which splits into two threads upon being copied, not one which follows along with one of the two copies.

Yes, very true. Sorry though, I guess I wasn't clear with the thread idea. I was trying to contrast your "flipbook" concept of consciousness with the thread concept, and ask whether they would actual feel any different. My own thought is: No, there's no way to tell them apart.