The books that I mentioned discuss many kinds of signaling, not just sexual semiotics. Sometimes people wear uncomfortable shoes not to look hot, but merely to avoid looking like a proletariat.

At this point I picture the stereotypical goth pickup line "Nice boots ... wanna fuck?"

Don't high heels affect a woman's posture and therefore apparent body type? So if high heels are under discussion, then they can increase the quantity of guys saying "Man, her body is so hot!" which, while stilted and awkward-sounding, is a common sentiment.

About once a year, I see men on Facebook complaining that trainer shoes are unsexy and that if women give a damn about erectile dysfunction which is such a big problem nowadays they should stop wearing them.

All the time. Or they don't know what it is, but they're reacting to the traditional presentation (heels).