Is it plagiarism to copy someone else’s material node group? By this I mean build the node group from scratch on your own computer based on the original creator’s post. What would constitute proper citation in a situation such as this?
There’s always a chance that two people can come up with the same node setup, or something very similar. Unless it’s something fairly complex of course. The decent thing to do, would be to cite the individual you “copied” from. I don’t know if there’s any legal implications though. I’m not a lawyer. So I couldn’t comment on that.
On a personal note, it wouldn’t really bother me knowing someone copied a node setup I’d created. But there are some who might. If they put enough time and experimentation into it, I can see how it annoying it would be for someone to not at least acknowledge the source. 
Thank you. I haven’t been using Blender for that long so I’m still copying a lot of materials.
i see it from time to time in premade testures , some tillable or not
even some of my work
Most is people tagging things on “pintrest”
then others repininning it and others reusing the re-re-repost
as for node set up
cite the original if you have not made MAJOR changes to it
or even if you have – be nice to others