New International Version
Nor should there be obscenity, foolish talk or coarse joking, which are out of place, but rather thanksgiving.
The Greek original can be used positively or negatively.
Thayer's Greek Lexicon
STRONGS NT 2160: εὐτραπελία
εὐτραπελία, ἐυτραπελιας, ἡ (from εὐτράπελος, from εὖ, and τρέπω to turn: easily turning; nimble-witted, witty, sharp), pleasantry, humor, facetiousness ((Hippocrates), Plato, rep. 8, p. 563a.; Diodorus 15, 6; 20, 63; Josephus, Antiquities 12, 4, 3; Plutarch, others); in a bad sense, scurrility, ribaldry, low jesting (in which there is some acuteness): Ephesians 5:4; in a milder sense, Aristotle, eth. 2, 7, 13; (ἡ εὐτραπελία πεπαιδευμενη ὕβρις ἐστιν, rhet. 2, 12, 16 (cf. Cope, in the place cited); cf. Trench, § xxxiv.; Matt. Arnold, Irish Essays etc., p. 187ff (Speech at Eton) 1882).
The word εὐ-τραπελία literally means "good-turn" to metaphorically denotes witty humor.
Let's see the context:
3But among you there must not be even a hint of sexual immorality, or of any kind of impurity, or of greed, because these are improper for God’s holy people. 4Nor should there be obscenity, foolish talk or coarse joking, which are out of place, but rather thanksgiving. 5For of this you can be sure: No immoral, impure or greedy person—such a person is an idolater—has any inheritance in the kingdom of Christ and of God. a 6Let no one deceive you with empty words, for because of such things God’s wrath comes on those who are disobedient. 7Therefore do not be partners with them.
Paul's tone is rather serious here. The good-turn witty humor is appreciated by non-believers. When it is along the line of obscenity, there is no place for any of such witty humor. Paul upholds a high standard for Christians.
Is it a sin or is it just inconvenient?
For Paul, such a person is an idolater, worthy of condemnation.