If Markdown were less static, you wouldn't have to find random implementation-specific documentation describing custom features - they'd be defined in the spec.

If Markdown were less static, you wouldn't have to find random implementation-specific documentation describing custom features - they'd be defined in the spec. You also wouldn't wind up in situations where two different Markdown implementations interpret the same Markdown text in two different ways, which happens surprisingly often. Markdown text is therefore always written for use with a specific implementation, and can't realistically be used as a text interchange format in e.g. email or any other federated system with multiple rendering implementations.