Seems like the RMT spammers have found a way to locate their characters outside Central City while still being counted as being in the sector. This allows them to send RMT spam messages that everyone in Central City is forced to see with no way to block or report them as they are too far away for the Nearby Characters menu to show them.
Multiple screenshots to show the spammers aren't simply somewhere high up or low in a corner somewhere; see the arrows on the speech bubbles pointing in the speaker's direction.
And just to be clear these are not from the control room either; that is underground but it is directly below the tower. The control room was empty and while there the spam still came from the same direction, way out to the west/south-west of town.
I don't know if there's any way we can report spammers that do this. They're too far away for their characters to show so we can't click them, and they're out of range of Nearby Characters. If NGS has a feature like ARKS Search, I'd be wary of using it since these spammers might start using the names of real players to both hide and cause false reports. Any potential reports using such a method might also provide less immediately-bannable detail than clicking a nearby character which presumably includes the chat log more accessibly.
This really highlights that the Nearby Characters list should simply include all characters in a sector rather than being limited to an arbitrary range that's severely smaller than the infinite-within-a-sector chat range. Alternatively we should be able to report chat messages directly from the Chat Log window, rather than needing to physically find their sender or get close enough to be able to use Nearby Characters.
On the bright side, if spammers are doing this now, it suggests all our efforts to report them in Central City are effective. At least effective enough that they're willing to try boundary-breaking with their disposable spam accounts to test Sega's automated detection and see if it's slower than bans that come from player reports.