Quote Originally Posted by AssertnFailure
Nope....terribly insufficient as proof.

Conversely, let's think of it this way:

1) Kakashi says MS takes a toll on the user.
2) Itachi is impressed by Kakashi's observation.
3) Kakashi asks how bad Itachi's eyesight has become.
4) Itachi freaks out.

Now, if we were to assume that JaySee was right, then #3 does not present anything that #1 doesn't present, right? So why would Itachi's #4 be so dramatically different from #2? It just doesn't make any sense!

However, if we consider #3 to be metaphorical in that it implies Itachi has failed to observe something important, then it does become new information, which justifies the drastically different #4 response.

In addition to this, I find that the confirmation that Kakashi does, in fact, have MS when he used it on Deidara further supports my point, because it allowed us to know with absolute certainty that #4 was a foreshadowing to Kakashi's new ability. With that said, where does the connection exist between #4 and Kakashi accusing Itachi of going blind?

Sometimes I think you guys need to take some basic courses in literary techniques.
But here's the thing , with all that being said, you seem to be ignoring #1 and #2 alot and focusing alot more on the sudden change in Itachi's expression in between #3 and #4.

Ch 257, p. 8
Kakashi: Not only does it use up a huge amount of chakra, It would seem the jutsu carries a great deal of risk for your eyes too, doesnt it ... Itachi.
Itachi: Having fought me once, you have made quite the analysis
Courtesy Shannaro scanlation.

This establishes that Itachi's eyes are indeed at risk, regardless of what type. I hope we can all agree with that.

Then this risk can either be Itachi going blind from using MS OR something else.

Case 1: Itachi's eyes are at risk in some other fashion and he isn't going blind

If this is the case, then what you suggest makes perfect sense and the blindness should be interpreted as just a metaphor and nothing else.

Case 2: Itachi is going blind from using MS

Sub-case 1: Itachi already believes that when Kakashi first mentions the risk to his eyes, he is referring to blindness.

In this situation, the sudden change in expression b/w #3 and #4 can once again be the result of Kakashi using #3 to suggest that he has acquired MS from right under his nose, and at the same time also taunting Itachi on his condition.

Sub-case 2: Itachi believes that all Kakashi knows is that MS puts your eyes at risk.

Then the sudden change between #3 and #4 can be result of Itachi being astonished that Kakashi knows the exact nature of of his problem (which can only be known through personal experience and Kakashi having acquired the MS himself)

Does all this definitively prove Itachi going blind? Absolutely not.
But it does suggest that Itachi going blind is a possible outcome and does not, in any way, conflict with the exact nature of this conversation between Itachi and Kakashi.

I think MS posing a serious risk to Itachi's eyes is an undisputed fact. And when most of us think of such a risk, we think of blindness. The fact that kakashi later mentions blindness, be it metaphorically or otherwise, seems to solidify the idea a bit more for me.