Comment by eternityforest

I never knew self plagiarism was a thing until recently. Is it a formality, or is there some kind of reason it's dishonest in the way normal plagiarism is?

Is it because it messes up the ability to figure out what analysis was done when, and what you had access to at the time, and makes it look like older work has the same trustworthiness as newer work that might be done with different equipment or access to sources or new experience?