I think Forth counts, in a "Turing-complete" sense of homoiconicity. A Forth program in a classic indirect threaded system can self-modify, reach in and change core interpreter words during execution. But it isn't obeying any formal soundness principle, since it's just a thin layer over the machine.

Compiled Forths might opt to wall off some of those options behind the compiler interface, in effect making the language slightly less far-reaching.