Can a theme or plugin change markdown-parsing?

Hi,
I want to change the default output of every default markdown table.
Is there any way to change the generated table element to include my class (e.g. "my-table-style")?

Yup, it's possible. I think the event you will want is onPageContentProcessed as the Markdown has been processed at this point, but the output is not yet cached. You could get the content, run some regex replacement to add your class and set it back as the page content.

You can look in the smartypants plugin to see how this is done.

Thanks a lot! I will try this out.