re: #414 Olsonist

Nuh uh.

If the singular possessive is difficult or awkward to pronounce with an added sibilant, do not add an extra s; these exceptions are supported by The Guardian,[17] Emory University’s writing center,[18] and The American Heritage Book of English Usage.[19] Such sources permit possessive singulars like these: Socrates’ later suggestion; James’s house, or James’ house, depending on which pronunciation is intended.

In both of those, the final s has a z sound. With “Jess’s” you would actually pronounce it like that.