It’s been displaced, pretty much, 18.5 million Google hits for Meh versus 3.5 for Feh. According to the Urban Dictionary, “Feh is a word used in many contexts. It is much like meh, but more agressive [sic]. It is used sometimes in place of meh, although this is largely inacccurate.”
I don’t know why a word that is “much like” another word should rarely be used in its place, but whatever. I’m guessing, and it’s only a guess, that, for whatever reason, gentiles know “meh” and not “feh,” unless it’s just Jon Stewart, trying to find another way to make up for the fact that, no, “Stewart” is not his real last name. Anyway, I won’t end this post by using either “meh” or “feh,” so don’t even worry about it.