I've been trying to understand the joining type logic that categorises a Mongolian letter as isolated, initial, medial or final, and the consequent effect of free variation selectors.
As far as I can tell, it is currently supposed to be controlled by the property joining_type. However, this property appears only to have been non-trivially assigned to the characters of the Mongolian script from Version 6.3.0. How was categorisation assigned before then? I am particularly interested in the intended effects of U+202F NARROW NO-BREAK SPACE and U+180E MONGOLIAN VOWEL SEPARATOR. They seem to presently have a Joining_Type value of Non_Joining, but some things would make more sense to me if they had the value Dual_Joining. I am wondering if their effective value has changed; e.g. previously the definitions for Mongolian characters worked as though they were dual joining, but when matters were formalised they accidentally became non-joining. Richard.
