My paranoia is coming on hard. I can't help thinking that they added the dialogue bug to slow down the big content mods until Dawnguards PC release. Especially now that the navmesh bug is no longer an issue.
Oh the scathing shame, for Bethesda Softworks to be routinely implicated of such heinous acts.
I doubt that even they think that any expansion-sized mods are coming out within the next months. Then again, Moonpath to Elsweyr might count as one, but I don't know of any others that are right around the corner.
And not being able to edit vanilla dialogue isn't really an issue for mods that take place in new lands with new NPCs. In fact, the dialogue bug cripples things like the Unofficial Patch, even though Bethesda 'left bugs in the game' so they could 'leave fixing the game to the modding community', as is often said around here. On the other hand, leaving the navmesh bug in with no forseeable fix would've effectively stifled any significant project, keeping their illuminati voodoo deal with Microsoft safe.