I have, on countless occasions, witnessed the bug that a follower and I attribute to WP-Typography: If you type any numeral followed by neutral single or double quote, the plugin converts that to numeral followed by, respectively, feet ′ or inches ″. The plugin thinks you are trying to write down measurements, but in the real world the plugin fires spuriously when a quotation simply ends in a numeral. (The plugin gets things very wrong when you try to write, say, six foot four inches in neutral quotation marks, resulting in 6'4″, which is wrong two ways.)
I have a great many screenshots of this phenomenon, many published on my Twitter @borkedunicode account (and the small group called Borked Unicode on Flickr). The error endlessly replicates itself through RSS onto platforms like Flipboard, where large Helvetica Condensed type makes things painfully obvious.
There is no reason for this substitution whatsoever. Neutral quotes are “wrong” in a pluperfect way, but spuriously-substituted foot and inch marks are wrong in every way. This feature of the plugin, if actually causing the error, should not be there in the first place and should be removed.