Am I permitted to play Mah Jong on Shabbos/Yom Tov?
My apologies but I am very familiar enough with this game. From my research it seems that it is similar to game of memory, or rummy, which are permitted on shabbos. This is not an issue of borer. If it is being played for money, or in a gambling setting then it should not be played on shabbos. Additionally it cannot be played on a computer on shabbos.
Shabbos Khalocho (Farkas) 12-124, Minchas Osher (R’ O. Wiess shlit”a) Shabbos Letter 6.