All control nodes which are stateless (eg. the cable_expr node) are automatically polyphonic, but the others should have dedicated support for polyphonic states.
I just checked in the source code and the input_toggle does in fact only have a monophonic state, but the compare node should be polyphonic. However I just realized that the wrapper code doesn't propagate that info to the UI to show the [poly] suffix like with the other nodes.
So:
input_toggle is polyphonic now
all control nodes properly show the [poly] suffix (it shouldn't have affected functionality though, was just an UI glitch).