Reddit's default fonts and font sizes don't look great on Linux, this userstyle tries to improve it a bit. It sets the main font to Open Sans and tweaks a number of elements fonts to be bigger.

It also tweaks the font settings for elements that RES creates.

Note: you will need to have the Open Sans font installed on your system. You can get it from here: https://fonts.google.com/specimen/Open Sans (click on Select This Font top right, then click the Family Selected tab bottom left, then click on the download icon in the tab top right)