Interesting. I hadn't seen that. It's not just a format though, it defines a lot of behavior as well. I think we may offer some guidelines for Ren library behaviors, but I don't want to head down the path Hocon has. And some things just seem like a bad idea. e.g.:
// this is an array with one element, the string "1 2 3 4" [ 1 2 3 4 ] // this is an array of four integers [ 1 2 3 4 ]
It did remind me of something on a Units type format. They talk about n^2 vs n^10 byte values and, e.g. the kilo vs kibi prefix or kB vs Ki. For byte units, my thought was to do something like binary! where you would do KB2 or KB10.
I wish there was a page with side by side JSON vs this for example.
Map comments (also posted in Gitter)
I'm considering both  and () as list and map brackets for Ren. What I haven't considered is the newer concept of allowing any value as a key. If Ren supports that, does it even need a separate map type? If Ren requires set-word keys, Red can directly support Ren maps, but not the other way around. Red maps would have to become Ren lists. If we do that, we lose the ability to distinguish them from parens when exchanged via Ren.
The idea of allowing () for lists is that it makes Ren more Redbol compatible, as well as flexible for those not used to square brackets. We may decide that more constraints are better, at least to begin with.
There is nothing that says Ren has to require pairs of values either, though there is certainly merit in that. We could just as easily say that a leading # before a list is just a hint.
e.g., if there is no map hint, the loader should never try to coerce the result to a map, if there is a hint, the loader decides what type to coerce to based on contents. If there is no outer list, as in a streaming scenario, there is implicitly no hint.