[Zope] python expression dtml-var rendering

[Trevor Toenjes]

Why do
<dtml-var mycontent>     and
<dtml-var expr="subfolder.mycontent">  render differently?

<dtml-var mycontent>   displays intended without HTML tags.  But,
<dtml-var "subfolder.mycontent">    displays as if it is a text file.

'mycontent' is a DTML_Document.
For testing I copied the same file to 'subfolder'.

But, <dtml-with subfolder><dtml-var mycontent></dtml-with> renders
correctly.
I thought this was the same as <dtml-var expr="subfolder.mycontent">

I assume this has to do with using a python expression, but surprises me in
behavior.
TIA for a quick refresher.
-Trevor

BTW, is there an HTML equivalent to fmt=structured_text?   like fmt=HTML