Indeed - in the electronics world such things have been known for years - those strange lumps on computer video cables and so on contain ferrite rings, for the same reason -well sort of - as much to keep interference out of the video or sound as well as to keep power supply interference inside the wire  as it were. Although on thicker wires the ferrite is quite often shaped as atight fitting tube longer than the hole up the middle  is wide, rather  than thin wire turns wrapped around a ring - and that may well be a better approach for solar panel wires too given your comment about inflexibility. Actually if you take a hacksaw and open an off the shelf filter 'brick' like the one I linked to above, a decent chunk of magnetic material in some shape or other is a large part of the weight of any reputable make. The rest is capacitors and sometimes a surge arrester or two. It is much cheaper to buy the ferrite cores separately, but you need to know  what you are doing to roll your own then.

But certainly the 'what to do if there are radio problems and how to avoid them by careful layout ' needs to be better advertised to the installation folk doing the job - I suspect many would be out of their depth.

Mike

PS

It is important that as far as possible the flow and return currents pass through the same magnetic path,  as then the filter core is only magnetized by  the unwanted out-of-balance component of the currents we want to dissipate and the core is not at risk of being saturated as it would if it only enclosed a single wire carrying a large current.

It also means that the inductance is not part of the wanted current loop, and does not affect normal operation in any way. 

In a fault the magnetic material saturates and the inductance 'switches off' at a low current (sub-amp for most suppression ferrites)  so any current required to blow a fuse flows essentially unhindered limited only by the wire resistance in the normal way.