Sublime Text 1 used OpenGL (1.1 only, hence no GLEW) and Direct3D, while 2 and 3 are mostly software only.
While Sublime Text 2 and 3 do use Skia, only a tiny fraction of its functionality is actually used, just for rasterizing lines and blitting images. Font rendering is done by using the underlying platform APIs to do the glyph rasterisation.
Wow, thanks for responding! Very impressive work.
It seems Jon comments on hacker news about once a year. So you win the hacker news lottery!