Repro case: data:text/html;charset=utf8,<div style="font-family:Tahoma;font-size:400%;">%D9%87%D9%94 Actual: The first part from right is distanced from its base (Arabic Heh) Expected: Like Chrome and Firefox, it should be near the base letter. AFAIK this is a font bug, but HarfBuzz on Firefox and Chrome have done some workaround for it so it can be considered ComplexPath/CoreText thus Safari bug.
Created attachment 295496 [details] Screenshot: Firefox, Chrome, Safari
The sequence of codepoints is U+647 U+654
Created attachment 295530 [details] Sample project Sample project shows that the problem is in CoreText.
<rdar://problem/29408071>
It is fixed apparently. Thanks!