- 1.) That's what this struggle, this isolation, this retreat is all about.
ON FIRST BLUSH: Yes, it does seem that a comma is missing in that example; and that your analysis looks solid to me.
The commas in the example seem to be bracketing commas, where they are bracketing supplements which have the appearance of having the form of an appositional construction. That is: there are two expressions -- "this isolation" and "this retreat" -- that are supposed to be supplements (whose ultimate anchor is the expression "this struggle"), but the last expression is missing its ending bracketing comma.
It seems that your example sentence ought to be punctuated as you suggested, for the reasons that you suggested. That is,
- 2.) That's what this struggle, this isolation, this retreat, is all about.
BUT . . . see below
On second thought, there is another possibility. Having read the comments to the OP's main post, it now dawns on me that the three expressions could be in the form of an asyndetic "AND" coordination. That is, the original sentence has the meaning of:
- 3.) That's what this struggle and this isolation and this retreat is all about.
And if that was what the author wanted as their interpretation, than the original punctuation of version #1 is, er, appropriate. But as this thread has demonstrated, the author's choice of punctuating this sentence seems to perhaps not been the best choice after all.
At the moment, I'm thinking that the author probably did mean to have the interpretation of version #3, for when I was analyzing version #2 earlier, its reading didn't quite seem right to me -- it seemed a bit weak -- and I thought the author would've tweaked it to make it stronger.
So, my current answer is that the original punctuation of version #1 is what was intended by the author -- the commas as used are for asyndetic "AND" coordination (and are not used for bracketing supplements).