A student considering graduate school in philosophy writes:

I was hoping to receive comments on the attitude of admissions committee members towards the attempts of a letter-writer to defend a weak element of a student's packet. For example, when professor X vouches for student Y, despite Y having something like low GRE scores or a poor mark in a core philosophy course. If the letter-writer goes on to explain why such blemishes should not immediately disqualify an applicant, will committee members take such reassuring remarks seriously? That is, can such remarks really serve as justification for why a weak element of an application should be discarded? Or does skepticism about the potential of the applicant often creep into the picture in cases where the letter-writer has to defend the applicant in some way, shape, or form? Are committee members worried that the letter writer might be inflating a student's performance by downplaying a smudge on an application? Lastly, is it even appropriate to ask a professor to defend weaknesses in your application? Or should one simply let the rest of the application do the talking? 

My own view is that such explanations are worth offering if there is something pertinent and substantive to say:  e.g., "Y had the flu when he took the GRE," or "his grades last fall were anomalous, no doubt due to the death of his mother."  Comments are open; what do readers think?  (Signed comments strongly preferred; all comments must include a valid e-mail address, which will not appear.)