My “childhood nostalgia” is definitely BC/WotLK, but when I think of my fondest memories of WoW, it was after I transferred to an RP server around the end of Cataclysm.
I think one of the most memorable moments was the night before WoD release, when everybody (it must have been hundreds of people, Alliance and Horde alike) went to the Dark Portal and set up medic stations and had soldiers taking turns on the front lines keeping the Iron Horde at bay. You’d be fighting the endless forces for a while, and then somebody would come and tell you they’d cover for you while you got healed up by the medics in the back line. And then when you had finished RPing getting patched up by the medics, you’d get back out there and tap somebody else out.
I love my community haha. To me, that was one of those distinct moments that had me really understand how lucky I was to have discovered the beauty of RP servers.