That's definitely a concern. The growing modern understanding is maybe that you cannot have consent in a power imbalance, and sometimes a lot of the "code" work right now is as much finding and signaling possible power imbalances as much or more than establishing even a broad consent signal. Consider pronoun signaling as one first example where it may also signal an unobvious power imbalance (though not necessarily in every case; part of the normalization work behind pronoun signaling is that if everyone does it, for many people it signals a status quo/no change in power dynamics).
Though also an interesting counter-note to me is that the handkerchief code itself was commonly used in BDSM cases intended to signal the consensual creation of a power imbalance and asymmetry, and it is in (mixed gender) BDSM communities where I've heard most of the less publicly documented, but possibly more generally useful, successors to handkerchief code can be found. So asymmetric power structures have always been intertwined in the opt-in signaling, even if yes some of the early symmetry was probably a necessary bootstrap state.
Though also an interesting counter-note to me is that the handkerchief code itself was commonly used in BDSM cases intended to signal the consensual creation of a power imbalance and asymmetry, and it is in (mixed gender) BDSM communities where I've heard most of the less publicly documented, but possibly more generally useful, successors to handkerchief code can be found. So asymmetric power structures have always been intertwined in the opt-in signaling, even if yes some of the early symmetry was probably a necessary bootstrap state.