Every once in a while I come across a post that warrants the ban hammer. Usually, a moderator edits the post, adding a line indicating that the post is inappropriate. However, the original post is left unchanged, ready to offend anyone in its path.
If a post is determined to be offensive, can the content also be removed?
That's at the moderator's discretion for that forum, really. You can PM a moderator from that forum and have it changed, and we'll be happy to do it. Or you can PM a red or blue.
The point of leaving the post intact with a note that an infraction was given is that people can see what types of posts are unacceptable and learn from others' mistakes. If it's just something mild (like calling someone an idiot or whatever), it's better to leave it as an example.
If it's something very offensive (extremely bad language or pictures), though, as Badpaladin said, PM someone and we're happy to remove it.