Sounds like I would need to make/find a specific tool for Markdown Here, and have the current Markdown bundle use that. I've been browsing through the Markdown Here Github code but I don't see how to implement it in TextMate. Could you be more specific on what I would have to do?

Martin Kühl wrote:

On 5 July 2015 at 10:21, Angelo Varlotta <angelovarlotta@gmail.com> wrote:

What I have noticed is that the default Markdown bundle doesn't support some
syntax features of Markdown Here in the Markdown Preview, such as tables and
strikethrough for example. Is there a way of adding these extra Markdown
Here features in the current TextMate bundle so that they are properly
viewed in the Preview? I've tried to use the redcarpet Markdown bundle and
the Github-flavored Markdown bundle versions, which present some
highlighting within TextMate itself but fail to make the preview work as
well. I've noticed that one can add MathJax support with the preference
option TM_MARKDOWN_MATHJAX set to 1. Is there something like that for extra
Markdown Here syntax support?

There is!
If you install a tool that processes “Markdown Here”,
you can set TM_MARKDOWN to the path to that tool,
and TextMate will start using it to render previews.

If you don’t set the variable, TM defaults to the original Markdown.pl,
which only supports the classic syntax.

Cheers,
Martin