Hi CB - To be fair Christ I believe is talking about his whole Physical being not a sign. He is talking about an imposter as a person.
We can also apply the following verses it seems to me.
Why does this generation ask for a miraculous sign? I tell you the truth, no sign will be given to it (Mark 8:12).
An evil and adulterous generation seeks for a sign, but no sign will be given to it except the sign of the prophet Jonah (Matthew 12:39, 16:4).
I would also caution that the Anti Christ and the False Prophet will also use miracles.