ok tally, but if you go in every topic and give an answer that appears useful to you, in specific topics, some people are probably going to find this answer pretty obvious because if they go on a forum to find specific info about a subject, it means that they already know the basics of that subject and it means that they googled a bit to find it, so you can expect this kind of answer.

About copying pasting a map, what you say is half true, in map porting, it's never that easy to port a map (unless it's on the same engine of course) so no fool can do it, but it's true when you copy paste something you can't take a lot of credit for what you did because someone else did the real hard job.I'm not OK with what you say about recreating a map from nothing, it's not at all a creative task, it's even all the opposite, but indeed it needs talent. Imagine a chinese dude reproducing a hundred of "la joconde" perfectly, would you call that being creative ? skilled maybe, but not creative.
Remaking a map from scratch is not better than copy-paste, you are still not being the author of it (so you can't take credits for it), the quality is, most of the time, 10 times worst than the original, and it's not accurate. At the end, if you want to do a good porting, you'll have to take elements from the original map, like the textures or sounds, so why not try to copying the whole thing ?

I found this on a cod forum but no one ever did it the other way (cod to source) :
http://ugx-mods.com/forum/index.php?topic=2997.0