Hi Michal

> Of course not, I am impressed that you understand it at all. All .4ht
> files are generated from literate sources available here:
> http://svn.gnu.org.ua/viewvc/tex4ht/trunk/lit/

I'm actually discovered the literate source after a while, but as you 
say it is largely only structurally literate ... not that many helpful 
comments inside (if any) that make you understand why this or that has 
be done in a particular way.

So yes I can see why you would normally start from working with the .4ht