abbreviation, initialism, acronym, hurrah.
Look, you don't go capitalizing words just because you truncated the word, not in an language on Earth that I'm aware of (and definately no matter what some web site like that says).
If you did, then I'd be calling SAM like yelling at him, you would point loudly at that MOUNT over there, and pretty soon we'd be celebrating XMAS by sending EMAILS over the NET.
Acronyms are capitalized specifically to indicate that the letters stand for other words. People starting capitalizing mod because it started to become a marketing term and/or they were feeling particlarly L33T that day. As someone who mods frequently, I'd prefer we stopped yelling the word typographically.