<p>Fair use of student-written academic papers surely includes (a) grading them, and (b) checking for cheating. To that end, I would be confident that posting segments of a paper in an academic forum for purposes of soliciting help in confirming originality (or not) is fair use. The contrary position would be truly silly.</p>
<p>I was accused of plagiarism my first year in college for something that was 100% original work. It worked out fine. I was able to convince the teacher that I was capable of having written the paper, despite his doubts, and that I had in fact written it, and of course having done that I also won a fair amount of respect from him. But it would have been nice if there had been easy ways for him to check obvious plagiarism back then.</p>