Of course, it is absolutely important to quote all thoughts that did not originate from the author. This makes one think that it would be OK to include works of others when referencing them correctly.
For example, consider that one had that really great list of problems that also apply to your own paper. Is it legal and/or legitimate to write about that list, include the key points in your work and reference the original author?
I am facing that situation where I want to include some key aspects but quoting all of them and describing them individually feels like copying too much, even though I explicitly state that the aspects originate from another paper with referencing to it.