Unusual as it is for me to say this, I agree with MobBoss on this one. When a passage of text is attributed to someone as a quote it must be word for word what they said - no adjustments however they're highlighted, no omissions. It is particularly unacceptable to reverse the meaning of a person's statement, whether by altering the text or by selectively removing words.
If a quote is attributed to a specific user, it must be their words, otherwise you are simply impersonating them. Even with a little disclaimer that it's a "fix" under a post (which frankly isn't a very appropriate attiude from a mod to start with), people skiming through the thread are likely to believe that MobBoss originally said that. There really cannot be any leaway on what is permitted in quote tags, since it leaves the misquoted user open to accusations of making statements which are probably the opposite of their viewpoint, and may well be offensive.