Notably, powerline ethernet destroys nearly the entire HF range, from 3 to 30MHz. This isn't just bad for radio hams, it ruins shortwave and some AM radio too.
The issue is that as you and others use powerline ethernet, you leak electromagnetic interference patterns back into the powerlines. This buildup of interference from multiple homes creates problems around your area, even if you don't notice it yourself.
Except unless you have some sort of an impedance follower you'll probably just end up attenuating your powerline networking to the point of not working.
How did that ever make it past FCC certification? I understand unintentional QRM from cheap things but that is something that's spec'd out.