[whatwg] markup as authored in practice

[Mike Schinkel]

Lachlan Hunt wrote:
>> (IE's disastrous XML Data Islands and Custom Tags 
>> provide sufficient evidence of that.) 

Why are XML Data Islands disasterous?  I Googled for "XML Data Islands" and
found nothing but articles praising it.  I Googled for "disastrous XML Data
Islands" and "XML Data Islands considered bad" and found nothing relevent.
Why would it not be a good idea to allow wekk formed XML to reside within an
<xml> tag?

Lachlan Hunt wrote:
>> Personally, I would rather see such things left for 
>> use in XHTML only, since browsers that support 
>> them are highly likely to support XHTML as well.  

How would that apply to, say, a mathematics forum implemented in HTML5 that
allows users to include MathML in their forum posts?  Or a Wiki implemented
in HTML5 for use cross-institutuions for math professors to collaborate?
Or...?

-Mike Schinkel
http://www.mikeschinkel.com/blogs/
http://www.welldesignedurls.org/