Well, that was something.... I have used ligatures in my code editor for quite a few years now, and I have NEVER been confused about the ambiguity this person is so upset about. Why? I have never ever seen the Unicode character for not equals in a code block, simply since it is not a valid character in any known language. In fact, I have never even seen it in a String where it actually would be legal, probably since nobody knows how to type that using a standard keyboard.
This whole article felt like someone with a severe diagnose have locked in on some hypothetical correctness issue, that simply isn't a problem in the real world.
But, if you for some reason find ligatures confusing, then you shouldn't use them. But, just to be clear, there is not a right of wrong like this blog post tries to argue, it is a matter of personal taste.