I just want to make sure that I understand this issue correctly. My situation is that I developed a chapter of my master's thesis as a chapter in my PhD dissertation. It is a substantial revision but they do have some overlaps.
I did some research online about self-plagiarism. Here is something I find that is confusing:
(1) Many people say that if my dissertation includes part(s) of my master's thesis, I need to cite them correctly otherwise it would be self-plagiarism.
(2) I also see many people publish chapters of their phd or master's thesis as single articles directly without being criticized as self-plagiarism.
To me, this obviously shows that the reason why most people take case (1) to be self-plagiarism is not about copyright of the master's thesis. If it were about it, then the case (2) should have been self-plagiarism too.
The most reasonable conclusion for me seems that case (1) is not self-plagiarism, but something to avoid nevertheless. Because one wants the PhD dissertation to be something new and something representing one's doctoral research. But if so, I see no reason not to include a substantially revised chapter in my master's thesis in the dissertation, because the substantial revision represents my doctoral research (and my committee agrees).
Am I right? Is there anything I missed here? Thank you.