Created attachment 8580544 [details] Screenshot of আদিত্য চোপড়া - Wikipedia User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:36.0) Gecko/20100101 Firefox/36.0 Build ID: 20150305021524 Steps to reproduce: Open this page: http://bn.wikipedia.org/wiki/%E0%A6%86%E0%A6%A6%E0%A6%BF%E0%A6%A4%E0%A7%8D%E0%A6%AF_%E0%A6%9A%E0%A7%8B%E0%A6%AA%E0%A6%A1%E0%A6%BC%E0%A6%BE Actual results: The combining character sequence “চো” in Bangla MN doesn't rendered correctly. “চো” in Noto Sans Bengali is correct. it is below of the page. Expected results: “চো” in Bangla MN is rendered as in Noto Sans Bengali.
Created attachment 8580565 [details] Screenshot from Firefox 36 on Fedora 21 Why is this a problem in Firefox itself and not with your installed fonts or webfonts delivered? No problems on Fedora 21, see screenshot.
This is a longstanding bug with Firefox rendering certain Indic AAT fonts; see bug 686225. (It's really a font bug, though it doesn't show up in all circumstances, depending on the font features used by the application -- unfortunately, the way Gecko manages font shaping causes it to hit this bug.)