it will just be attenuated / the signal will be weaker.
And by "weaker" he means it'll work on the bench or at your feet, but not at all when you get any distance.
The attenuation from polarity mismatch is VERY severe. The low range attenuation you feel at short range is deceptive -- it follows a square-law effect.
On the positive side, you can stand next to a big metal building and the reflected signals will come in clear . . . sorta . . . except they're probably scrambled and attenuated a bit in the bounce . . . pretty much what you want to filter out using the polarity
As for your helical antenna . . . spin the coil the other way and it's reversed. If you build your support structure in two flat pieces (like cross-hairs), flip one and it's reversed the thread. Then reversing the polarity is a matter of flipping your template, bending some more wire and de/resoldering the feed line.