Δαφνη Ευτυχια Αρθουρος

I'm used to handwriting it, and I usually print in all-caps -- and seeing it printed was usually on a blackboard where, again, everything but variable names and funsction names often got written all-caps, so my instinct was to type it "IFF" ... Until I looked it up a week or so ago and saw (as someone else pointed out in a comment to the poll) that in uppercase it usually means "identification friend or foe" and the dictionary used lowercase for the math usage.

But I'm not sure how much that convention matters, since it'll almost always be obvious from context which meaning is intended. I haven't decided whether to go back to uppercase for "if and only if" yet ... if I do so, the only reason will be what you just described: it makes it a little clearer that it's not merely a typo of "if" (which I agree with you about).