Some people use the archaic spelling "shew" but only the senses "to prove or demonstrate". Or again in mathematics "rng" to mean a ring that does not necessarily have an identity. Or "iff" to mean "if and only if". These would look like inconsistent typos to nonmathematicians.

Or "referer" in HTTP because that's what the standard uses. Or "creat" when discussing the UNIX system call or a function with the same purpose on another platform.