sml.tcl passes that test easily :-)
C:\JFL\Temp>"echo.exe" "<p><u>underlined</u> <i>italic</i></p>"
<p><u>underlined</u> <i>italic</i></p>
C:\JFL\Temp>"echo.exe" "<p><u>underlined</u> <i>italic</i></p>" | sml
p {u underlined ;i italic}
Yes in a few quick tests that I tried, it did seem to round trip,
however to be honest I could not find any xml in the (thousands) of
xml files I have to hand where the sml would be easier to edit than
the xml.
given a syntax like
<p><u>underlined</u> <i>italic</i></p>
I can easily move from one element to the next, rename or comment out
whole elements etc, and given a schema get auto completion on the
allowed elements at any point and red text if I mistype an element
name.
To edit a large file using a syntax like
p {u underlined ;i italic}
would be scary, essentially the whole thing would be seen by any
editor I have as an unstructured string and I'd be responsible for
getting all the {} and ; in the right places.
If I had to produce such a syntax I would much prefer to edit a source
in xml and generate that syntax at the end (same true of json)
David
