Those may not be the only ones. Implementations would need to:
- support Unicode parsing, which, depending on the tools you use, can be cumbersome (e.g. javascript in the browser)
- know (or infer, but that may not be acceptable) the encoding of the input text, whereas it can currently just deal with ASCII chars and ignore others with a lot of very common encodings (e.g. UTF-8, ISO-1559-*…)
As for the rendering of a list bulleted with • , you can add two spaces at the end of the lines so that it would still get a line break. While I get that it is not what you want, you can get your “output ≥ input” with only a minor inconvenience.