Perhaps I misunderstood. But let's say I do run uMatrix in deny more, I get the site HTML as the Tim Berners-Lee intended. Yet that already may contain some kind of advertising material, so to view only the actual content I'd need to have e.g. an XPath do it. So I would have a database of sites and XPath (or other ways) describing how to find the content, instead of describing how to get rid of non-content.

Can I tell uMatrix to only show a certain XPath from the page? If so, I agree it is a content selector, albeit pretty impractical :).