Question: The other day, I strategically did not do a Joker exchange. Another player made a big deal out of it as if I’d made a mistake. Is there a rule that requires me to do a Joker exchange?

Answer: There is no requirement to do a Joker exchange. In some cases, a player may choose not to do a Joker exchange if they want to prevent another player from being jokerless.  If they are going for a jokerless hand, doing a Joker exchange and then discarding the Joker would provide valuable information to the other players. However, if there is still a symbol tile available to someone else, it might be wise to consider taking the Joker to prevent another player from getting it. 

Source:  Mah Jongg Made Easy 2024, page 23 #1