This pull request recommends using only characters in the unicode braille patterns set as well as html whitespace for renderable text (as best as I could define that). I don't know that we want to make it a stronger restriction as there may be some cases where non-braille characters are needed. I mentioned mathml in the note, as I expect that would be one case (but let me know if I'm wrong).
It also clarifies that this recommendation only applies to the default rendition if adding multiple renditions.
This pull request recommends using only characters in the unicode braille patterns set as well as html whitespace for renderable text (as best as I could define that). I don't know that we want to make it a stronger restriction as there may be some cases where non-braille characters are needed. I mentioned mathml in the note, as I expect that would be one case (but let me know if I'm wrong).
It also clarifies that this recommendation only applies to the default rendition if adding multiple renditions.