There will be a time, many times, when you’re not sure how you should reply.
It might be someone has said something smart-arse to you, gave a bit of a sly dig, made a profound comment, or attempted to trap you with a bit of cleverness.
In other words, though they haven’t asked a question as such, a reply could be useful if you could figure an appropriate one.
Except, you’re not really sure what yours response should be?
You might only have a half formed thought, something that even as you think it you know is not on the money. Anything at this stage would be lame.
So shut up.
Stay shut up.
Don’t fill in the gap with words – especially if you’re struggling to form even semi-decent ones.
This retains an ambiguity within the other person.
They can’t tell whether you’re pissed off, whether you’re cool in not bothering to reply, or simply digesting the comment for whatever reason.
In actual fact, this is essentially the same as an old adage:
Better to keep your mouth shut and appear to be a fool, that to open it and remove all doubt.
Nobody’s quite sure who coined this expression, as debated here in quite a lengthy entry at Quote Investigator. Sources as diverse as Mark Twain, the Bible and Confucius among many are given as its originator.
Whatever, it is a similar idea – when you don’t know what to say, say nothing.