Parsing HTML is MUCH faster then parsing XML.

> Parsing HTML also takes time, and there must be support for markup
> that is not well-formed, since a significant fraction of deployed HTML
> is ill-formed. Since the capabilities document is small and will
> likely be machine-generated, it is less likely to be ill-formed. Also,
> since this is a new format, there is no legacy of ill-formed content
> to contend with.

most blogging tools produce well formed content, but there already is
lots of working code that deals with this. Nothing new is needed.
Parsing HTML is MUCH faster then parsing XML still. I have had lots
perf analysis done on this.

DOM and Dumber

"all major web development platforms have high performance HTML
parsers that present the document as a DOM. XML parsing is common,
but is more complex than manipulating a DOM, and another thing for
the developer to figure out."