Complete and utter bollox. You shouldn't be allowed to post on forums with lies like that.
I am sorry, but I also didn't believed it until I actually heard it. The mains wires in my appartment were pieced on every couple of meters, and at each junction there were devices connected to wall sockets etc etc., the usual mess. Wiring in an independent and uninterrupted supply from the fuse box to the audio wall socket made a difference comparable to upgrading from a Nait3 to a NAC52/NAP250 on the old supply (which ironically backups well your own opinion as I understand it). And the guitar amps sounded way more natural, deeper, cleaner, faster. Interestingly a new mains wiring costs way less than upgrading the amps.
The whish to prohibit posts about my personal experience / opinion would be not exactly the most democratic whish I gues...? And you want to decide that what I wrote is a "lie"...?