What do you consider to be bad quoting habit? I am always quoting parts that I try to reply to. I think that I would have failed in your test on many levels, but on the other hand I feel that I improved a lot since I joined the forum. My mistakes that I know of are my bad english and that my posting history is full of bounties (although I am going through my posts once or twice a month to delete the expired ones).
Jet Cash talking about full quotes when user don't remove irrelevant parts of quote, images and other content. It's also not advised to quote OP.
I think it's ok what you are doing. For example now you didn't quoted full original post, but only part of it that you're replying to.