JOKER EXCHANGE WHEN PLAYING CONCEALED (Article 77)

Commentary:  When a player has chosen a concealed hand, they are entitled to do a joker exchange just like everyone else. 

Question from a player:  Can you exchange a joker from an exposure if you are playing a concealed hand? 
 
Answer from the NMJL:  “Playing a concealed hand does not negate doing a joker exchange.  You are only prevented from calling a discard when playing a concealed hand unless the tile is for mahjongg.”

Source:   National Mah Jongg League Bulletin (2020)

Others answers from the NMJL: 

“You may take a joker from any exposure whether you are playing a concealed hand or an exposed hand.” 
 
“A joker exchange always may be claimed whether playing either a concealed or an exposed hand.” 
 
“You may do a joker exchange when you are playing a concealed hand or an exposed hand.” 
 
“It does not matter whether you are playing a concealed hand or an exposed hand.  You may always replace a symbol tile for an exposed joker.” 
 
“You may always exchange a tile for a joker, regardless of whether you are playing a concealed or an exposed hand.”  
 
Source for other answers:  (2004, 2010, 2011, 2018, 2019) https://www.nationalmahjonggleague.org