What bugs me is that in the typical scenario, the person who is receiving the mixed signals and confused ("Alice") usually does absolutely nothing to show their attraction to the other party "Bob". - So, what, they are supposed to do all the work and put their dignity on the line before you make a move? Especially because, if they ever do hook up, it's shown that the whole reason Bob gives mixed signals is because Alice showed no attraction. The trope is usually done when the confused party is female, but done often enough with men that it gets really old fast. Of course, this applies to many romantic tropes so...
It's contextual. In Inuyasha Miroku gropes other girls, but repeatedly shows feelings for Sango; is it really Sango's fault that she doesn't respond to someone who will risk his own life to save hers one minute and ask a total stranger to "bear [his] child" the next?
In fact when you get to borderline-tsundere territory the reciever may end up confessing feelings to someone who actually hates them. And then you get to the sender sending mixed messages simply because they don't know their own feelings.
My answer, then, is that the person sending the mixed messages just stop sending mixed messages. Otherwise they shouldn't complain when they don't get a response.