Sure, I can understand starting your response by quoting a phrase or comment from another's post - you want to emphasize that you're addressing some particular portion of the longer post.
But I can't, for the life of me, figure out why people feel that's it's important to quote the whole OP all over again? Does anyone re-read the entire re-post a second time? Or third or fourth time? I highly doubt it. So why put it there and clutter up your response?
I'm not losing any sleep over this useless re-posting, but it does make threads longer than need be and more scrolling has to happen. It just seems like a time waste for everyone.
Does this puzzle anybody else or am I just weird (wait . . . don't answer that)?