Can it be modded in Linux?
Depends on what you mean by Modded... Being that it's an online game, the file changes are very limited and strict. Some of the text based files can be modded, which is where most of the problems seem to be, in the settings. That plus, as far as I know, we can't use D3D and have to force opengl on both the game and Linux :p
The game itself DID have a linux version several years ago that the game devs (at Blizzard) used.. but it was never public.. and they themselves stopped using it ( X( ).