Yes, this is an old one it seems, every where I look the issues concerning xhtml compatibility is closed. or cantfix . argument: xhtml pages are rare. Just because people implement them wrong does not mean no one builds xhtml pages. due to the usage of PHP's DOM Documents saveXML() I am forced to use the correct xhtml definitions. Meaning I have to tell the browsers that i am outputting xhtml+xml.
most xhtml+xml questions and tickets where concerning FCKEditor. so I assume i am in my right when asking why CKeditor does not work on xhtml+xml pages or when you are going to implement the compatibility (since I couldn't find any details concerning the new major release you seem to be planning according the roadmap page on the developers section). I really hate to start using TinyMCE or anything else that is not CKEditor, since CKeditor is the most simple to use editor.
why I'm using DOMDocument?? I implemented a way where I can define per page which scripts or stylesheets there are going to be used without the need of using functions in areas of the html. this way I can easily create plugins (add metatags or even add div elements for social media for instance!) without the need of adding stuff to the html file since it is being done dynamically.
most xhtml+xml questions and tickets where concerning FCKEditor. so I assume i am in my right when asking why CKeditor does not work on xhtml+xml pages or when you are going to implement the compatibility (since I couldn't find any details concerning the new major release you seem to be planning according the roadmap page on the developers section). I really hate to start using TinyMCE or anything else that is not CKEditor, since CKeditor is the most simple to use editor.
why I'm using DOMDocument?? I implemented a way where I can define per page which scripts or stylesheets there are going to be used without the need of using functions in areas of the html. this way I can easily create plugins (add metatags or even add div elements for social media for instance!) without the need of adding stuff to the html file since it is being done dynamically.

Re: Content type xhtml+xml
Documentation Manager, CKSource
See CKEditor 5 docs, CKEditor 4 docs, CKEditor 3 docs, CKFinder 3 docs, CKFinder 2 docs for help.
Visit the new CKEditor SDK for samples showcasing editor features to try out and download!