On rare occasions, there are very difficult to handle posts where I would want another moderator to look and make the decision, so that the action is not unilateral.
An example of such which came up recently is a comment which I find offensive or nonconstructive, which also specifically references me. Since there might be a conflict of interest if I were to take the action into my own hands, I would want another moderator to look at it.
I decided to flag the comment, and it simply deleted it. This created far more problems overall.
I am aware that using the moderator chat would be an alternative solution, and I plan to use this in the future, but currently I don't understand why a moderator flagging a comment deletes it.