Talk the talk
Now, most of us who call ourselves Christians do a pretty good job of avoiding immorality (“fornication” in some translations). We also do well in staying away from pornography, foul language, and pagan sacrifices. We may still be working on completely exterminating greed ("covetousness") from within ourselves (a very strong temptation in modern society), but we think we’ve got it pretty much under control.
But since when is “silly talk” a sin?
There is a good case to be made that St. Paul is primarily talking here about silly talk when the Christian community comes together for worship and thanksgiving (“which is out of place”).
Even so, we should take heed of St. Paul’s warning not only in Church but also throughout our lives.
Why? Because, as St. Paul says, we are to “be imitators of God.”
That is not to say that we must be dour and unhappy – quite the opposite! As Christians, we have an infinite number of reasons to be happy, to rejoice, and to celebrate.
What we must do is strive to make everything we say and everything we do reflect our Lord and Savior Jesus Christ: his love, his holiness, and his truth.
How do we do this? Not by fretting and obsessing, but by asking for his grace, building up our spiritual lives, and remembering that at every moment in our lives, with every action and every word, we have a wonderful opportunity to be imitators of God.