While RestartResponseAtInterceptPageException already works correctly with Ajax requests (e.g. user is redirected to a login page), continueToOriginalDestination() forwards the user to the Ajax request URL (user will get a <ajax-respons>...</ajax-response> on his screen)
Improvement: The user should rather be forwarded to a proper page.
Workaround: A custom PageMap implementation
However, as the method setUpRedirect(RequestCycle) is private, deriving from the default PageMap will require some ugly copy-paste in order to do so. This could be avoided by a) making setUpRedirect(RequestCycle) protected and/or b) introduce a protected method that constructs the interceptContinuationURL inside setUpRedirect(RequestCycle).
The custom behaviour could be: Redirect to the page the Ajax request belonged to. Or even better: redirect to the Ajax call and render the complete page (well, don't know how tricky that would be).