Tab characters are handled differently from current implementations

[roop]

Tab characters should be expanded based on their position in the line, similar to how text editors do tab-expansion (like 'set expandtab' in vim). This is how almost all current implementations handle it. Handling unexpanded tabs in the parser is possible and more correct but complex, and potentially inconsistent with almost all current implementations.

The syntax guide (user documentation) should also be updated to reflect this. Particularly, the syntax guide should not mention optional tab-based syntactic constructs (i.e. instead of "use 4 spaces or 1 tab", just say "4 spaces").

Ref: http://six.pairlist.net/pipermail/markdown-discuss/2013-October/002956.html