Ok, I'll try to answer to your questions.
This language is a proprietary program used to perform corpus (textual) analysis. It's an expansive piece of software targeted to just a bunch of scholarly individuals. Even though everybody is used to XML in this field they decided to use a "simplified" syntax and even went as far as developing their own "linter".
As far as I know their is no clear syntax definition either backus-naured or informal. It's just "hey, the anchors/tags look like ". Actually the manual of the program uses Comic Sans MS as title font.
Now, this syntax is indentation insensitive. There are examples in the manual that feature such a behavior. The scope of type-X tag ends where another type-X tag begins.
Concerning colors, the tags (both type and value) are displayed in red (or whatever color I might use), the actual text is fine (white). I was wondering if their was some convention in the way to name patterns so that they get displayed in different colors, but after some careful examination I think I might be able to handle this on my own.
Back to the folding heuristics : I actually got it working as I wished on one, clean, well-indented file but not on some indentation-less file. After some tests it turns out it works ONLY IF it is indented, so I suppose i must be relying on some sublime-text/textmate specific heuristic since I did not specify anything about indentation in my tmLanguage file.