Re: Itachi could have killed Obito...
The thread states that, with knowledge, Itachi could have killed Obito.
Then the question is... Why didn't he?
Itachi loved Konoha. Obito was a threat to Konoha, Sasuke and the whole ninja world. Three things that Itachi tried to protect. Konoha was the village he loved, Sasuke is obvious and the whole ninja world? By massacring the Uchiha clan to prevent a 4th world war, and stopping Edo Tensei.
All Itachi would have had to do is locate Tobi and take him down in battle. If Itachi were to keep locating Tobi if he were to keep phasing away from Itachi, soon enough he'd have to engage in battle.
With knowledge, Itachi would have won...
Well, the thing with that is it's kind of the THING your SUPPOSED to do with ninjas is to keep your techniques and yourself secret from anybody that could be an enemy. Telling your opponent your abilities gives them the ability to find counters. If you learn something about somebody, you'd be stupid not to use it against them in a life-and-death battle. So the whole "knowledge" thing is a weak argument.
So Tobi finds out that pressure in the air current builds when someone uses Amaterasu, and then when Itachi uses it, he is just supposed to sit there and say "Oh, well I wasn't supposed to know this. It doesn't work in Itachi's favor. I'll stand here and take it".