Is a lightweight carbon paddle a worthwhile investment for a beginner?

Absolutely, the paddle weight is more important in many cases than the boat weight. You hold it up the whole time. Of course appropriate blade design and paddle length also have a huge impact on the pleasure of the early paddling experiences. Later of course, we begin to sort out our personal preferences, but in the beginning we don't know enough to do that yet. Therefore, some truly sound advice from another paddler or sales person who is considering your needs rather than pawning off their own preferences is vitally important.