Just my humble opinion on how Inkscape reads SVG files, is to be very forgiving on input file parsing. In case of a minor format violation, try to correct it. Report the worst errors, of course. And then do Inkscape's best to generate clean and proper data. Thus, over time, Inkscape has a side effect of gradually mending a domain of broken files. A lot of editors do it this way.

Do we want to reject an XML file if it is horribly munged? Sure. But if it merely needs a bit of tender care, then allow it. Then instead of merely telling users to fix their file, Inkscape does the fix itself. Use validation to tell people why their file has a problem. But don't always reject it.