shop=mortgage has some usage at taginfo: https://taginfo.openstreetmap.org/search?q=shop%3Dmortgage . It maybe that one of the more popular other shop tags is more appropriate; take your pick: https://taginfo.openstreetmap.org/keys/shop#values .
When I was looking at the list of what to render in that line I found the list at line 2664 in https://github.com/SomeoneElseOSM/SomeoneElse-style/blob/master/style.lua#2664 .
