What JSON is
JSON is a text format for nested data: objects with named keys, arrays, strings, numbers, booleans and null. It has no date type and no comments.
Every web API, most configuration files and anything that talks to JavaScript.
What Textile is
Textile marks header cells with |_. and data cells with plain pipes.
Redmine, and older Rails applications.
What changes when you convert JSON to Textile
Four shapes all read correctly: an array of objects, an array of arrays with a header row, an object of column arrays, and an object keyed by row id. A single wrapper key holding the array, which is how most APIs reply, is unwrapped automatically. Nested objects are flattened one level into dotted keys; anything deeper is kept as JSON text in the cell, because a table cannot hold a tree.
The header row is written with the |_. marker so it renders as a header.
What carries over from JSON to Textile
JSON records 4 things about a table that Textile has no way to hold.
JSON distinguishes a number from the text of a number; Textile does not, so every value arrives as text and has to be re-parsed by whatever reads it next.
An empty cell and a missing one are the same thing in Textile, so a null and an empty string in the JSON both come out blank and can no longer be told apart.
JSON can hold a value that is itself a list or an object. Textile has only flat cells, so nested values are flattened into one cell rather than being spread across columns.
A line break inside a cell ends the row in Textile, so line breaks are replaced rather than carried through.
Textile marks header cells differently from data cells, so the keys are lifted out and written once as a marked header row rather than repeated on every row.
The identifier 007 comes out of the Textile as 007. Reading it as a number would have made it 7, and an id that changes value is worse than one that stays text.
The role "Analyst, data" survives with its comma, in one cell rather than split across two. That is the first thing to check in any converted table, and the usual place a Textile file goes wrong.
The quotes around Jonah "Jo" Pryce are left as a plain quote character in the Textile.