While looking for interesting tags to watch, I happened to notice that we have both sumer (currently with 15 questions) and sumeria (with 3 questions), both presumably referring to the bronze-age civilization and region of Sumer in southern Mesopotamia.
I'm tempted to just edit and retag the three questions tagged with sumeria but, given that I'm a relatively low-rep user on this site, I thought it prudent to check for community consensus first.
I've posted a self-answer describing my proposed plan of action below; you're welcome to either upvote it or post your own answer describing what you feel should be done instead.