Comments
I've worked for a company where the official, written down and enforced coding standard (C for embedded applications) at some point somehow mutated from "Code should be self-commenting," which is all well and good, to "Code should be self-commenting, if you need to add comments you should instead rewrite your code to be self-commenting." The result of this was that comments started to become shunned like gotos in code reviews and gradually disappeared almost entirely.