Should I report a PhD student’s incompetence to their supervisor? I had a short exchange of mails with a PhD student who wished to ask some questions about a paper of mine, which was troublesome in many respects:


The student had a blatant lack of basic knowledge and techniques of their field. (Imagine a computer scientist not knowing what object-oriented programming is, a mathematician not knowing what fields are, etc. They did not change fields for the PhD.)
The student should be able to answer some of the questions with very little work.
Initially, the student did not give me even remotely the information I needed to answer their question in a useful manner.
The student seemed utterly overwhelmed with their project.
There were strong hints of a “do my work for me” attitude.


For the purpose of this question, assume that I am very likely correct in my assessment.
Going into details about why I arrived at this conclusion would be beyond the scope of this question and be disclosing too much.
I also wish to make clear that I am not annoyed by the questions or similar, I am just worried about the situation.

I am now wondering whether I should write a mail to their supervisor (whom I don’t know and who is not at my institution) informing them about this incident.
My considerations so far are:


I am pretty confident that this student will not finish their degree (by honest means).
As long as they continue with this, they waste time and resources: their own, their supervisor’s, and other researchers’ whom they are emailing.
If I were this student’s supervisor, this is something I would like to know since it can prevent me from wasting my time and resources on them.
On the other hand, I hope that I would quickly notice these qualities in a PhD student.
This problem will likely escalate soon anyway.
It’s the supervisor’s job to talk to the student and give them the possibility to clarify in case I misjudged them.
However, if I am wrong, my information may wrongfully harm the student if the supervisor overreacts or the student’s image is tainted subconsciously.
Depending on the situation, such a communication as mine may allow the supervisor to smoothly get rid of the student – which is good if I am right and the student is incompetent, but bad if I am wrong.


My question is this: Is there anything else I should take into account when making this decision? (I know that, at the end of the day, I have to weigh the arguments myself.) Note that I already sent a mail to the student but am skeptical whether they got the message.
Emailing the supervisor and saying "this student is incompetent and you should get rid of him/her" would come across badly, for a few reasons:


You lack the information to make a holistic assessment of the student.
Even if you're right and the student is weak, weak students can improve.
The supervisor and their institution undoubtedly have their own methods of quality control.
Most importantly, it's not really any of your business.


It's nice that you made a good faith effort to answer the student's questions, but if the exchange has become annoying for you, your best recourse is to simply stop responding and forget the student exists.