Follow up to this M.Y. question.
I think that I have seen Rash"i or perhaps the Gemarah use this expression, occasionally, Loosely the phrase translates as:
"The one that understands will, and the one that has insight will be silent."
I might be mistranslating some nuance, here in one of the words. However, I am curious as to why someone says this and what message their trying to convey. Usually, when I see this phrase, it has followed to rather complex explanation of something, and I still have trouble getting the gist of the explanation. It's as if the commentator is saying, "Well, most people won't really understand the point here, anyway."