I've been reading a lot of posts on this site and noticing that several ppl quote an entire post - sometimes the main post - to reply to. Is that really necessary? Isn't it kind of understood that you're replying to either the main post or the post directly previous yours and anything else is what may need clarification?

Or what?
And what's editing anyway?
BTW I know everyone is going to try to be clever and quote my post. At least the first person to do it can claim originality, even if it's not true.