According to the commentary wiki page, this tag should be used "on posts where the artist commentary is understandable by the average English speaker", either because the commentary is in English or because it "consists of symbols or something similar." This seems to me to indicate that symbol-only commentary is understandable to English speakers by default, and therefore there shouldn't be any reason why symbol-only commentary shouldn't imply the commentary tag. Is that right?
Updated by RaisingK