PhD course grade impact on postdoc and fellowship applications? This past spring was the second semester of my PhD program. A professor of a core course refused to grade my final assignment because it was late after deadline had been extended. The professor had read and provided feedback on various drafts of the manuscript throughout the semester.

However, I only missed the deadline because of an emergency. A couple of days before the deadline I had to drop everything I was doing to tend to urgent institutional review board (IRB) issues. On the day the manuscript was due, my  old thesis advisor emailed me demanding to withdraw a presentation from a national conference immediately until IRB exemption was granted. This was more urgent than submitting the paper because there were serious legal implications attached. 

Thank goodness the Chair of my Doctoral Committee was made aware of the issue. I spoke to the Chair, who suggested I explained to the professor I had an emergency and even told me to drop their name. I did just that, but the professor still refused to  accept the paper and gave me a C+ (38.9/50) without counting my final. I also explained the emergency situation, to no avail.

I don't want to push too hard on this matter, but I am very worried that a C+ will prevent me from receiving fellowships and getting a good postdoc position in the future.  For those of you out there with first-hand knowledge of the impact PhD-level course grades have on one's career, will a  C+ diminish my chances of getting a fellowship and being strongly considered for competitive postdoc positions?
In my field (math), nobody looks at your grades, so this will not make any difference. 

A personal anecdote: I had a first-year grad course with a tough grader who gave me a B- in a core subject. This did not affect my trajectory in the least; I still passed my quals ahead of time, I wrote a thesis and graduated on time, and I'll be starting my post-doc in the fall.