Icon fonts don't degrade gracefully when someone (ie me) disables "let websites use their own fonts". Either you get meaningless letters or those little unicode squares - neither of which are actually useful, of course.
Additionally, icon fonts rely on the PUA to render their glyphs. Given the emoji explosion over the past several years, that PUA is getting harder and harder to assign glyphs to.
I can't be the only one that's visited a site on my phone and found emojis where an icon font glyph was meant to be.
I can't be the only one that's visited a site on my phone and found emojis where an icon font glyph was meant to be.
See probably the most famous example: https://www.etsy.com/teams/7720/bugs/discuss/14559563/