A lot of attention has been given to "isolated grounds" for computers and the like. This also a real market sor surge suppression and UPS (back-up power) systems.
While not required by code, nor ever mentioned in the specs for any such system, it is my practice to NOT share the neutral between separate circuits.
By running a dedicated nuetral, I avoid the whole harmonics issue. More important, to me, is that I also eliminate one source of a voltage surge- a loose neutral connection. I'll even go so far as to identify the neutrals in the panel and junction boxes.
You are correct in your understanding of the code- this is just one area where I chose to go "beyond" code minimums.
