The patch to get rid of the topic from the URLs looked trivial. So I attempted it 😊
I just applied it here locally, and very brief testing shows that it works. I'll play slightly more, and then submit to the SDM. In essence, my patch just removes the topic variable from several calls to export_url_vars in three utility procs within tcl/bboard-defs.tcl, the main one being bboard_msg_url.