You opened with the claim that nonstandard analysis hasn't caught on because it's "mostly the exact same arguments wrapped in slightly different language". I pointed out that the arguments are in fact very distinct: e.g. Nelson's proof of the intermediate value theorem is something that any NSA student would see, but no standard textbook teaches IVT by a standard language counterpart of it.
One post later, you answered that Nelson's IVT argument is in fact the "standard nested interval proof" with the limiting step rewritten in nonstandard language.
That claim is simply wrong. Why? Because Nelson's construction straightforwardly generalises to Brouwer, while the nested intervals proofs cannot. The discussion of reverse mathematics / computability is not a tangent, it explains precisely why Nelson's proof can generalise to give the BFPT in two dimensions, whereas the nested intervals proofs (which you claim is the same) cannot.
You then brought up that the BFPT generalisation of Nelson's argument needs the Sperner lemma as "crucial additional ingredient". Now you make the same point again:
> What I'm saying is that for the coloring proof of BFPT to work, whether clothed in standard or nonstandard language, you must perform a combinatorial argument that uses a topology of a triangle as a necessary ingredient, similar in shape to the proof of Sperner's lemma.
Presumably you keep pointing this out because you think it justifies some claim like '1D Nelson is actually nested intervals with the limiting step recast in nonstandard language, even if the 2D generalization of Nelson is not'.
But it does not. The combinatorial content is the same, the 1-dimensional interval case uses the topology of the domain just as much as the 2-dimensional triangle case does. The 2D argument wouldn't work on the annulus, and the 1D version would not work on the union of two disjoint intervals. The Sperner lemma is present in 1D, and present in 2D. If instead your point is only that proving the BFPT requires a harder case of the Sperner lemma than IVT, then of course it does. But what relevance does that have to the original claim that Nelson's IVT proof is the nested-interval proof? The proof of the Sperner lemma is pure combinatorics, it does not involve any (standard or nonstandard) analysis.
Or have you changed your mind on your earlier claim that Nelson's proof is "is the standard nested interval proof"?
If so, I think that's great, and closes the thread on whether NSA is largely the same arguments, since even the first proofs of the basic results are different.
If you still think that it's the nested interval proof, well, I am not sure what else to say, apart from linking the literature which studies this exact question, that I've already done, and that you dismissed as a tangent.
Either way, this discussion went on for too long at this point, so I won't monitor it further.