UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/66.0.3359.117 Safari/537.36

Example URL:

Steps to reproduce the problem:
Place HTML tags within an Arabic word.

What is the expected behavior?
The letters of the word should be joined.

What went wrong?
The letters of the word are separate; adding ZWJs is necessary to join them. Even adding ZWJs isn't a full resolution, as ligatures aren't used then.

Does it occur on multiple sites: Yes

Is it a problem with a plugin? No 

Did this work before? No 

Does this work in other browsers? Yes

Chrome version: 66.0.3359.117  Channel: stable
OS Version: OS X 10.13.3
Flash Version: 

Here's a small discussion on this issue: https://twitter.com/KhaledGhetas/status/989311667682119681

Adding ZWJs per se isn't an an issue, but:
 - it's much easier to not add them
 - adding them doesn't render ligatures properly, like ألا
 - Firefox (and Edge, reportedly) don't need them.

Coloring parts of Arabic words is a often needed feature, like highlighting matches, adding tajweed coloring to the Qur'an (open muqri.com, click play, and click on the ت), and so on.

Canary (68.0.3409.2) behaves the same as Stable.
 

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