It sounds like you have a good intellectual grasp of the situation. A classic buddhist metaphor is the man who awakes and sees a poisonous snake on his bed and panics but then realises the "snake" is merely a piece of old rope. Likewise, the stories about the self, me, I, mine can seem very real and engaging but when we look clearly we can see that they are all empty symbols (mental words and pictures).
So when you say...
What is actually happening when you "take the thought seriously"? What is the difference in DE between observing a thought and being dis-identified from it and becoming caught up, identified with or taking the thought seriously?I take the thought seriously as a thing (in the material world, or nearly material), as opposed to just a symbol that represents an actual thing.
can you look to see if you can find the precise moment when you move from a state of dis-identified awareness to being identified with a particular (set of) thoughts?
I know I have asked you this before but perhaps it is worth revisiting. We can see the thought of an apple is different from an actual apple so it logically follows that thoughts of an I or self are not the actual self. So what do these thoughts actually point to? What does the word/thought I actually refer to?

