To answer Russian Violets
question of whether a poor student has ever asked for a reference from me, the answer is "sure, fairly regularly." Have I written them? Depends if I really
disliked them. But what about the student who is just not a very bright student? I have said more than once, "please remind me what I gave you for a grade for my class?" This sometimes works. For others, they smilingly say "oh, I think it was a C-." "And you think I would write you a good reference?" "Sure!"
If you ask me when I'm busy, I typically will say "fine" and write it.
If you ask me when I'm not, I might explain it to you SLO-O-O-OWLY.
Students, if you are reading this, consider yourself warned.
(h/t: Cold Spring Shops