View not rendered properly when HTML 5.0 Syntax is disabled.

Could you tell me which version of XWiki specifically you're using, and which servlet engine (tomcat / jetty)? HTML 5 being part of disabled syntaxes is the default behaviour AFAIK and I never had this issue I think.
Also could you check if you have same behaviour when checking the rendered diff of a standard page (by checking the diff between two versions of a page from the history tab).