Q. Our typesetter applied Chicago’s never-add-a-hyphen-to-a-URL-breaking-over-two-lines rule to hashtags breaking over two lines (specifically “#MeToo”), and the proofreader marked to force them all to one line, which may result in a lot of loose/tight lines since this occurs quite frequently. Would you suggest stetting the original, going with the proofreader’s fix, or hyphenating?
A. We would suggest the following order of preference: (1) prevent the hashtag from breaking (your proofreader’s preference); or (2), where a typefitting problem would be ameliorated only by a break in the hashtag, hyphenate: #Me-/Too. Many URLs contain hyphens; hashtags never do. So whereas it is important never to add a hyphen to a URL, lest it be misinterpreted as part of the string, it’s OK to allow an optional hyphen (also called a soft or discretionary hyphen) in a hashtag at the end of a line—exactly as you might add a hyphen to an ordinary word that would not otherwise include one. Furthermore, whereas a URL that breaks over two lines is usually recognizable as such without the aid of a hyphen (and in printed works, CMOS recommends breaking a URL immediately before an existing hyphen), a hashtag broken at the end of a line without a hyphen is subject to being misread as a hashtag (#Me) followed by a new word (Too).