[emersion]

>I think the text format for interleaving source and commentary needs its own discussion somewhere, and probably a standalone repository separate from implementation (and some day preferably too, an RFC, or at least a MIME type registration).

Yeah, this library just parses email threads and the goal isn't to define a new format. This particular output format is just for debugging and unit testing, it's not meant to e actually used as is. The library user just gets a tree of text fragments with metadata, it's up to him how the output will look like.