Please, let's refrain from such awkward terminology. "Graphic language", "visual language" are fine. "WYSIWYG data processing" is okay. But let's not forget any graphic syntax is an abstraction.
Yeah, I'm not sure how the term applies here. If you're using Luna to make a program that generates output, "what you see" (the node graph) is definitely not "what you get" (the output). Maybe you can have an inline preview, but it's not what you're editing.
WYSIWYG describes domain-specific tools that let you manipulate the final product directly (or a draft of it), without having to look at any kind of source, be it a node graph or source code.
An abstraction of what? If the paradigm is dataflow - i.e. capable of running directly on (hypothetical) dataflow hardware - a graphical representation is more natural than a textual one.
Please, let's refrain from such awkward terminology. "Graphic language", "visual language" are fine. "WYSIWYG data processing" is okay. But let's not forget any graphic syntax is an abstraction.