There's another similar subject: Chome will not join all Arabic characters as it should.
Simply because it assumes that fonts are mapping the compatibility characters for the joining forms, when there are such compatibility character encoded. But some fonts for Arabic don't map these caracters (those at end of the BMP), but instead map the contextual forms utdng the mandatory OpenType features on the standard Arabic characters. If Chrome cannot find those compatibility characters, no joining will be attempted, and the isolated forms will be displayed instead (without even trying to fnd a matching font that has those compatibility characters mapped, such as "Arial" instead "of Arabic Typesetting"). I found the case on some rare Arabic characters that normally have 4 contextual forms, only 2 were rendered (the isolated and initial forms, not the medial and final forms). I think this is a bug of the layout engine that does not use the FULL set of joining types (despite they are defined since many years for most characters that Chrome still do not fully join), notably of the Arabic letter follows a TATWEEN (in that case it should not be using the isolated or final form for the letter): Chrome or its renderer (tested on Windows 7) does not implement apparently one of the standard joining types (the *forced*" joining).
