Don't know if Joe Armstrong ever said anything like it, but I would propose naming an Erlang/OTP analogue of Greenspun's tenth rule (the one about C projects containing ad-hoc, buggy implementations of Lisp) for him.
Any sufficiently complicated concurrent program in another language contains an ad hoc informally-specified bug-ridden slow implementation of half of Erlang.
To be fair Elixir shows you can just use the BEAM if you want. If you need these semantics at this level there's very few reasons not to go this route.
