Apparently the bug is coming from TextAreaClass#getEditorType which is checking first the presence of "xeditmode" (in https://github.com/xwiki/xwiki-platform/blob/xwiki-platform-17.10.4/xwiki-platform-core/xwiki-platform-oldcore/src/main/java/com/xpn/xwiki/objects/classes/TextAreaClass.java#L328) and apparently this xeditmode is set to "text" in ClassEditSheet: https://github.com/xwiki/xwiki-platform/blob/xwiki-platform-17.10.4/xwiki-platform-core/xwiki-platform-appwithinminutes/xwiki-platform-appwithinminutes-ui/src/main/resources/AppWithinMinutes/ClassEditSheet.xml#L141 apparently it seems to be only for choosing the fields in the palette, but then the value remains in the context and we wrongly use it for the editor, leading to not resolving the syntax properly.
We should probably have a way to reset the xeditmode. Now this one seems to be exclusively used here, I'm wondering if we still need it at all...
