Ok. However, I publish all my code in plain text. Arguably this this is the normal way code gets distributed, unless you edit in word... The choice of font, syntax highlighting, editor, etc are personal choices, what is terrible for you might not be terrible for me.
You publish your code in plaintext, it goes to github where someone reads it through some fancyfying code formatter that github applies to it and which might not even do the same ligatures as your editor. I'm not saying this is a dire problem, or a problem with you or even this specific font - rather the idea of ligatures in program source code to begin with, somewhat similar to using code identifiers (as opposed to literals or comments) outside of ascii-compatible characters of unicode.
That's not a very good thing, especially considering that there are (probably ?) actual unicode characters '→' and '≡' that are not valid syntax for -> and === in languages that utilize the later.
Good for who? In an IDE the person reading them knows what don’t they are using, and so won’t get confused. The IDE itself knows what language the code is in and will highlight invalid syntax.