I think it depends. When writing a general answer to the original post (like I do now), quoting is probably unnecessary. When answering a part of the question or writing a reply to some of the later comments, it may be absolutely necessary to quote to avoid misunderstanding.
My general rule is that if I'm replying to the overall OP then I will just reply. If I am replying to some other post or some specific part then I will quote that post or part of that post.
That's right, I tend to do the same. There were a couple of long OP where I quoted to highlight a specific point I was answering, otherwise a simple reply will do.
