[DiapDealer]

Yes, thanks. We will certainly want to fix the crash regardless.

But with regard to malformed xhtml, the Reports feature is not the only Sigil feature that could be adversely affected by intentionally leaving things not-well-formed (though they may warn rather than ungracefully crashing).

Can you share an example snippet of a style section in an xhtml file that will make Reports barf on its own shoes? Or are you saying that any invalid style section causes the crash?
Never mind. I've tested myself, that nearly any non-well-formed xhtml will cause a crash when Tools->Reports is initiated.