Well, using the quote facility does make it absolutely clear just who one is responding to, RosiesMaw, but I agree that the use of it to quote and requote long posts does result in one conversation taking up a great deal of space. Especially if it's only one point in the original post that is being responded to.
Like you, I like to copy, paste and italicise the bit I'm responding to, and cite the poster I'm responding to, but I'll use 'quote' if the OP is just a short one.
But, everyone is different, I don't see how any 'rules' can be imposed for quoting from other posts.
I do find it confusing when people copy and paste but just put the 'quote' inside speech marks, which are easy to miss.
As for using 'quote' for a post that is just before your own response, sometimes other people have posted while I'm writing my response, so the response is separated from the post being responded to. Which could also be confusing...