Can coiling a Ethernet cable negatively impact the signal?

I like more this other answer: https://superuser.com/questions/475934/can-a-huge-coiled-lan...

The cable has pairs of wires that canny the current in oposite directions, so that must cancel most of the magnetic fields. An the pairs are twisted, that also should reduce magnetic flux problems.

And anyway, without a big iron/ferrite core in the center, I doubt you can cause too much problems.