MathML not displayed properly in firefox and thunderbird because it doesn't load the fonts

[n9]

Hello,
Not sure if this is a bug but I get `Request for font "Latin Modern Math" blocked at visibility level 2 (requires 3)` and such for other fonts in the console and the output just looks bad. 

Firefox and thunderbird's `\mathbb{R}` which looks like `<mi>ℝ</mi>` in raw html

  

Chrome's `\mathbb{R}` 

 

Dunno if this style is even intended. Help please!