@jjt The issue I see with only strictly `true` values is that most things people use as booleans are often not strictly `true` or `false`.

As for XHTML, I'm not sure if React is even compatible with it anyway (and who even uses it, hehe), if that is something we strive to support (do we?) then I would argue that it's better to detect it and *always* mirror the key in the value, rather than this weird in-between.