GFAQSSB, or gfaqssb, is a horribly naughty word that is a major Terms of Service violation on GameFAQs. Using that word will automatically cause the post to be flagged and not posted, because it's SUCH A NAUGHTY WORD, and so bannable!
In ancient times, cavemen discovered this word, which was exiled to Earth by ancient astronauts. They reveled in vice, making the word a part of them, and they eventually became corrupted. Before long, they became the evil force known as Nazis today. That's how evil that word is. If you say it too much, you'll turn into a Nazi.
Yes, the word is still considered very offensive, even to this day.
It was confirmed why here:
And thus this confirms that the mods are pussies that get offended by someones saying their waifu sucks. This is the internet you fucktards.