Not sure how it would help: here's the escaping is done entirely in frontend, when the request is sent the element are already removed. See my comment: https://jira.xwiki.org/browse/XWIKI-21866?focusedId=116717&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-116717

That happens when you insert a new macro call, but the problem is also when you edit a page that already has a problematic macro call. The font-end is simply applying the same type of escaping done on the server side. If we change the way macro markers are escaped then we need to update both places.

Would it help if we changed the (server-side) escaping of these macro marker comment contents to use HTML escaping?

I think it would. The alternative is to try to rely on CKEditor events to escape the XML comments before CKEditor "parses" the HTML, and to restore them afterward, before the macro plugin initializes the macro widgets.