This is a clone of 2972096 (https://sourceforge.net/tracker/?func=detail&aid=2972096&group_id=236865&atid=1101373), which was automatically being closed without an actual fix existing, and it seems that I do not have the permission to re-open that bug. I’m still using nagstamon and I am still very convinced that for me, a nagstamon that is only visible when something is wrong, is much more useful. Thus I again updated my patch to the latest version, including recreating the changes to the .ui (and manually cleaning up the mess that glade does when editing such a file). Hoping that maybe the patch can be applied after all or, if not, it might provide useful to others, I am attaching it here.
For reference, the corresponding Debian bug report is http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=579001