For Semitics at least, this is *not* a "left quotation mark"; people normally use a left half ring wherever the character is available.
The following is a small and quickly generated sample list of publications in which transliterated Semitic ayins are represented by left single quotation marks (and alephs are represented by right single quotation marks):
For Semitics, it could have something to do with what side of the Atlantic you're on... Library of Congress transliteration [1] uses apostrophes (according with their general tendency to use as little diacritics as possible), the DMG advocates half rings at least for Arabic, see [2]. French practice in most works I've got here is to use half ring; I've got one French work [3] where superscript lowercase epsilon is used.
Philipp
[1] http://www.loc.gov/catdir/cpso/romanization/arabic.pdf; http://www.loc.gov/catdir/cpso/romanization/hebrew.pdf
[2] Brockelmann, Carl et al. (eds.) 1935, Die Transliteration der arabischen Schrift in ihrer Anwendung auf die Hauptliteratursprachen der islamischen Welt. Denkschrift dem 19. internationalen Orientalistenkongre� in Rom. Leipzig: Brockhaus.
[3] Cantineau, Jean 1960, Cours de phonetique arabie, Paris: Klincksieck
