Why do Arabic characters behave as separate characters when styling single Arabic character?

Question

Basically what I am trying to accomplish is Arabic characters misuse highlighter !

To make it easy for understand I will try to explain a similar functionality but f

Answer 1

As Jukka K. Korpela indicated, This is mostly a bug in most WebKit-based browsers(chrome, safari, etc).

A simple hack other than the TAMDEED char or getting contextual forms for Arabic letters would be to put the zero-width-joiner (‍ or ‍) before/after the letter you want to be treated as single Arabic ligature - two chars making up another one. e.g.

عرب‍‍ي
  

demo: jsfiddle
see also the webkit bug report.