:Good question. WP:CANVASSING does allow "The talk page of one or more articles, WikiProjects, or other Wikipedia collaborations directly related to the topic under discussion." so leaving a note there with a clear edit summary as the locus of previous discussion would immediately catch those who watchlisted it. But that may be none. As far as directly notifying - there have been 3 geo RMs (which are the 3 at Talk:Cà Mau), and a 4th on the capitalization of Province at Talk:An Giang Province, provided there's no picking and choosing, that all 4 RMs (which will have some duplicate participants anyway) are notified it can't be seen as picking and choosing.