This seems to be aiming for completely different goals though. People use markdown as a text and word formatting system that is readable in plain text and easi

This seems to be aiming for completely different goals though. People use markdown as a text and word formatting system that is readable in plain text and easily transforms into HTML. The the main point you are driving to people in this thread are the custom tags which goes against the plain text readability and adds extra complexity in this scope. You are competing against HTML preprocessors that are primarily used for that reason - to be converted into fully fledged HTML. Markdown is not in this scope by any means.