I think the point is that a user wouldn't know they're overriding the design. When a user sets a uniform font, they're opting to not see whatever font the site was designed for, but it's not at all obvious to them that they'd be messing with icons.

But re-inventing things that already exist is also sub-optimal. Why create a font, why not use an existing standard?

Also, having a list of the icons together with their labels made it easy for me to know what they meant. Some of those icons would be baffling to me if they didn't have a label. I could be convinced that extra visual clutter is a good thing, but some designer is going to have to give a nice example.

That's not the point, I think. If the article proposed we all switched to using wingdings, it would get the derision it deserved.

Here it is my phone which is overriding your design, i can't see the icons