I doubt PR counted for much among deatheaters, so Dumbledore did not lose anything here, and for the rest of wizarding Brittain—they didn’t have a choice other than Dumbledore, so they wouldn’t believe deatheaters that DD could do sth like that. And later they would not change their opinions, but would forgot their motivation (because it was unplesant—fear of worse evil).
Very similiar thing happened in real life in WW2. http://en.wikipedia.org/wiki/Katyn_massacre Nazi Germany announced in 1943 that they have found mass graves of tousands Polish prisoners of war all killed by shot in the back of head by soviets. USA and UK had treaty with Stalin, and Germany was more immadietly dangerous, and Stalin was instrumental, so nobody believed Germans, and after the war Poland was sold to USSR, and only in 1990 Katyn massacre was made public.
Jumping in time just 6 hours back indicates to me that in the computer that is simulating MoR universe data is kept with 6-hours long cache.
As to Atlantis—they found a way to get out of the box—one level up, and they’ve left some cheat-codes for people that are still in this simulation. That also explains why some very important figures (like Dumbledore) think MoR runs on stories—somebody outside of simulation changes the simulation accordingnly. Maybe this simulation purpose is to make the best stories?
Also explains why prophecy works for more than 6 hours into the future—because simulation has some invariants, that make for best stories, and seers can well, “see” them, but only for very important events, and only guess ral meaning of these predictions. Hence mysterious prophecies.
What it doesn’t explain—why cheat codes are in latinised English.