Originally Posted by Hitch
I realize that you are definitely DA MAN, but, really: I NEED IT! I WANT IT!
Okay: if I ask, pretty please, could you at least stick in an option (The No Strippers option?)
The problem is, unsurprisingly, Tidy.
It flat-out deletes any element it's not explicitly coded to recognise, even in a bare-bones configuration. Since with HTML5 (which epub3 is going to use as the basis of OPS docs) content creators will be able to use even custom elements (say, <ducky> or <hitch>), I'm planning to rework Tidy so that it leaves unrecognised elements alone.
I've looked into it and it appears that doing it properly will take quite a bit of work. So it's on the list, but not before Sigil 0.4.0.