[juki]

The big difference between Markdown and the Org-markup is that the latter has syntax for various kinds of metadata, while Markdown is purely content. That metadata is used for things like task management, literate programming, spreadsheets, customizing export behavior, etc.

One could, in theory, create an extended Markdown flavor that allows similar metadata, but that wouldn't be compatible with any existing tools anyway, so there's not much point.

[indentit]

Pretty sure Markdown with metadata (sometimes referred to as "front matter") already exists and is called MultiMarkdown, no?

[juki]

By "various kinds of metadata", I don't just mean the document metadata (such as title, author, etc.), but also the metadata applied to specific elements such as the outline items, tables or code blocks.

For example, in Org you can add task management data, scheduling information and arbitrary properties to the outline,

    #+COLUMNS: %ITEM %TODO %ASSIGNED_TO %SCHEDULED %PRIORITY
    #+PROPERTY: ASSIGNED_TO_ALL juki some other people

    * TODO [#A] Some task with priority A
    SCHEDULED: <2019-04-20>
    :PROPERTIES:
    :ASSIGNED_TO: juki
    :END:

    Some description.

This defines a task with a custom property `ASSIGNED_TO` whose value can be one of ["juki", "some", "other", "people"], which can be viewed and edited in a column view. It could also be used by a custom export-backend or some other tool.

For another example, you can add formulas to a table,

    #+CAPTION: A table with formulas.
    | foo | bar | Row sum |
    |-----+-----+---------|
    |  10 |  20 |      30 |
    |  30 |  40 |      70 |
    |-----+-----+---------|
    |  40 |  60 |     100 |
    #+TBLFM: $3=vsum($1..$2)::@4=vsum(@I..@II)

Here the 10, 20, 30, 40 are added manually and the other cells are calculated by the sum-formulas. Since the results are inserted into the table, other tools can just skip over the TBLFM-metadata if they don't support it.