[quote=@IAmTheIsland]
Here's one

Extending creative disagreements/collaborative scisms, or however you want to word it, into personal beefs/grudges. 

We weren't on the same page creatively? Didn't gel in collaboration? 

Why make it personal? Unless there were personal insults/attacks made, of course. 
[/quote]
It is personal when you steal my character concepts, world building, and so forth. It's not legal plagiarism, but it is ethical plagiarism. 

Interpretations of character outlines or plot premises are not so much, but I have had people lift my sheet right after I exited a game and ceded all permission to their use.