When the locations of Upstab and Downstab are swapped, either when specifically enabling the option to swap or when the flag is 50/50, the related NPCs still provide their Vanilla text.
In other words, if the NPC in Mido gives the Upstab sword tech, he will still say that he's giving you Downstab, and the same is true for the NPC in Darunia. I do believe this affects community text, as well.
When the locations of Upstab and Downstab are swapped, either when specifically enabling the option to swap or when the flag is 50/50, the related NPCs still provide their Vanilla text.
In other words, if the NPC in Mido gives the Upstab sword tech, he will still say that he's giving you Downstab, and the same is true for the NPC in Darunia. I do believe this affects community text, as well.