Using encode_entities makes this sort of thing happen:
XML Parsing Error: undefined entity Location: http://XXX.YYY.ZZZ/
and points to the relevant entity.
I think using encode_entities_numeric would help a lot with this. This is just a naïve assessment, but this would prevent xml-like pages being non-xml.
I suppose you mean a html generator, and not a html parser.
ikiwiki uses numeric entities where required, but not otherwise.
It seems valid for xhtml to have eg,
<in it. Do you have a specific example? --Joey