h2+ headings are ignored in md.vm files

[Bukama]

Affected version

3.21.0 (current in maven-site)

Bug description

When writing md.vm files headings from second level on are ignored and not rendered - neither on the page nor in the TOC-macro.

From the following snipped

<!--MACRO{toc}-->

# Header 1

## Header 2

### Header 3

gets rendered to this

Workaround is some crazy

<!--MACRO{toc}-->

# Header 1

#[[##]]# Header 2

#[[###]]# Header 3

[slachiewicz]

## is a comment in Velocity processing, not much we can do

[hboutemy]

any idea?
better documentation than https://maven.apache.org/plugins/maven-site-plugin/examples/creating-content.html#common-issues-and-workarounds ?
like something more prominent in https://maven.apache.org/guides/mini/guide-site.html?

[hboutemy]

or any idea like hacking Doxia Renderer, that launches the Velocity template engine https://maven.apache.org/doxia/doxia-sitetools/doxia-site-renderer/
like "if source is markdown and we find ## at line start, warn"
= strange hack, but that may be adapted to the situation, as I can get that the current Velocity behaviour with Markdown content feels like a bug "content strangely disappears"

[slachiewicz]

Just an idea - change the comment decimeter? Instead of hash use something different or skip comments functionality?
Similar was with two dash - as separator for header properties