I would be real interested if someone would put scope probes into an outlet in a "normal" residence and give us a good picture of exactly what this "line noise" was and looked like.
Then one could 'harvest' it and actually see the changes... or not.
Same with the effect of power conditioners and such. Entirely too much arm waving and unsupported statements, and not enough effort put into what would be really simple tests. Alas, I am no longer in the job where I had access to such equipment