Of course a machine language is completely different to a human language (constructed or natural). A small example:
- in human language we can invent new words and expressions at will
and if they "catch on" they will be widely understood. in a machine language new expressions can only be designed in (top down).
Just because human language can't be standardised doesn't imply that machine languages can't.
MediaWiki syntax hasn't been designed top down, it's just had new features added whenever a developer felt it was a good idea - much in the same way as a natural language is created. Human languages can be standardised, there is just very little point, so no-one has a reason to learn the standard. Unless the standard is better than the alternatives in some way, the same applies to machine languages.
The main question is this: If I was writing a wiki engine and wanted it to be compatible with other wiki engines, why would I implement Creole instead of, say, MediaWiki syntax?