Another forum post explains this issue in even more detail:
From their post, I think this may help others understand who don’t get the big issue with this on RP realms:
"I’m sure it seems like a weird non-issue to a lot of people internally and externally, but having no sharding in population centers on RP servers makes our silly, nerdy hobby possible. Not just it makes it better, it makes it possible.
Otherwise our communities are fragmented and can’t see and interact with each other, it makes it impossible to hold large events or have populated cities.
It isn’t a matter of convenience, it’s a matter of having most of the people who play on Moon Guard and Wyrmrest accord, big swaths of people a lot of whom only subscribe to do this, through content lulls and without clamoring for new big expensive raids and generally dropping tons of real cash on transmog, mounts and pets, inclined to keep playing.
This always seems to take Blizzard’s internal team by surprise, that this happens, and it seems to always take a lot to get people to understand what’s happening and how to fix it. If there’s a better process we’re all ears, we’d love to have a more expedient way to have the issue addressed."
The sharding shouldn’t exist in the first place on RP realms and if that is non-negotiable, we need to have it turned off right after an exclusive event ends. As it is customary to be done - what is also unfortunately customary, is that the developer needs to be reminded to turn it off each time. It causes a lot of frustration for folks in the roleplaying communities.