If a new member comes to AB and sees people taking chunks out of each other, do you think they will believe this is a friendly and helpful place and want to stick around? Or if someone posts a question in Law or Family for example, do they really want to be judged, or did they just come here for helpful advice? That's why we remove rude, judgemental or offensive posts, instead of leaving them for everyone to see. That, and watching people arguing in News threads (for example) is very tedious.
Posts talking about or quoting the removed post are also removed because they don't make any sense after the first post has gone, and also because if we keep talking about a removed post, it defeats the purpose of removing it. That's why we generally don't enter into discussions about removed posts or banned members.
Moderators don't have to identify themselves, and removed posts are reviewed by the editorial team.
The bottom line is, we want this to be a friendly and helpful place, and posts that break the
Site Rules are removed. It's pretty simple.