I don't think there is an 'offline' version available, maybe in the future!
For the standard iterator notation is meant:
{iterator,min,max,delta}
{iterator,min,max} goes automatically to {iterator,min,max,1}
{iterator,n} start automatically from 1 (indexing is base 1 in Mathematica, so that makes sense).
{n} could not possibly mean {iterator} because then there aren't any bounds. so it must be a number of times. Later on they added the 'shortcut' so you can just write n, just to make it easier for starters I guess.
This notation works in Sum, Product, Integrate, Table, Do, et cetera...of course iterator in integrate has a slightly different meaning...
I'm not sure what you mean with "But curly brackets are still required to control a list of values".
The reason why position gives double curly braces back is quite easy: This needs to be like this because Position can also work on deeper 'levels', so the only solution is to do it the way they do it now; otherwise you can't always tell if they mean several parts or a single part multiple levels deep. It also designed to work along with Extract, rather than Part. It says this in the documentation:
Position returns a list of positions in a form suitable for use in
Extract, ReplacePart, and MapAt. The form is different from the one
used in Part.
Regarding ReplacePart, the second argument can be given as {3->x}
, but 3->x
as well, again this is just a shortcut, The difference here with Position is that there is no ambiguity, you can't interpret either of them in a 'wrong' way.
I'm not sure what you mean with your Fold example, but probably also logically explainable...