Sadly, nowadays thats pretty much everyone. If you want me to care about you (apparently/marketwise you don't), then get your design right. Tip: Design is not looking pretty. Design is this question: Does it work?
Turn off foreign fonts (?) maybe 0.001% of web users do that.
Fonts to display icons reduce HTTP overhead and scale, looking great on retina screens.
There are some very good reasons why you'd want icons in a font. For example, font rendering is well supported by all browsers and very configurable through CSS, and if the default font size is increased for accessibility reasons the icons can also scale.
> Why would you turn off foreign fonts?
Because I don't want foreign fonts. They are usually either just bad (e.g. worse than my OS font) or render badly.
> It's an edge case, 0.0000001%, ....
You are not downwards compatible. It's an edge case because you make it one by deciding on web "standards" by thoughtlessly applying these short-sighted idioms.
Using sprites instead of fonts to support users with foreign fonts disabled means degrading the product for some other users. Building a polyfill means not spending the time improving something else.
Why do you consider "support everyone" to be obviously better than "build a better product for a subset of users"?
I feel like the undending debates around this issue (most often regarding JS) exist because some people on HN look at it through a business angle where #2 can make complete sense, while some others look at it through a Web ideals angle where anything but #1 is heresy.
Edit: To be fair, the Web ideals remark doesn't seem to apply to you. You rather seem to consider than being pretty is way less important than supporting more people. But why? Being pretty has been increasingly important this past decade, and especially so regarding blogs where being pretty is one of the few differentiators.
Blogs are my newspapers, thats why. For me accessibility and downwards compatability outweigh the "product" a lot. I have a low-end smart phone for which most "products" are ununsable. Why do people throw away expensive hardware that woks perfectly fine? Because the modern software doesn't run on it.
Take for example the opposite: http://blog.fefe.de
That is a product that meets my demands: I can read on any device, using multiple clients. I could read this page with a dual-core as well as with a gameboy. Serve TTF font's, maybe I rather use bitmap fonts? Doesn't matter.
I could read that blog using Mosaic, lynx, w3m... kindle displays... It also works fine for braille terminals.
I guess I am more interested in powerful systems than the pityful products of the App-bubble. After all I am a programmer.