I have some perfectly safe code using them that crashes Intel icc. Useful if you ever need to, I don't know, crash icc I guess.

Among other things, this means icc doesn't run other compilers' testsuites, because I reported the same bug in the first release of clang and clattner fixed it right away.

And given that C11 made them optional, Intel can just close such bug reports with won't fix using the ISO as justification.

Not if it claims GCC compatibility, which it does. Though I believe the frontend is licensed from EDG anyway.