I wrote a lengthy mathematics paper that consists of about 8 sections.
For comprehensiveness and consistency purposes, I have a subsection that massively quotes one of my supervisor's papers (there is no other paper in existence that covers that subtopic in the same detail, I tried to preserve the original rigor and formulations, and that paper is simply brilliant). I stated what is being done at beginning of the subsection, and everything is properly referenced.
About half of the subsection is citations, and about half of it is my own text.
The supervisor was extremely happy with the paper, and I got great feedback from the faculty.
However, I'm a bit embarrassed by the massive citations in the subsection, and I am concerned that there may be an ethical issue with that. Normally, I don't quote any text in my papers (although of course I use references) -- the entire text is my own.
I would appreciate your opinion on this issue.