I'm honestly not sure what part of the question you would like me to clarify. If you can explain exactly what part or aspect of the question you would like me to clarify, I will attempt to do so.
Would you imagine that there are Christians whom the Holy Spirit never prompts to help poor people?
It appears that your view is that Christians do have a moral obligation to support the poor, but that moral obligation is bound on the heart of the Christian by the promptings of the Holy Spirit, rather than as a legal code of sorts. Please correct me if I am wrong.
I would probably say that the moral obligation to help the poor is part of the natural law binding on man as part of our nature and by way of God's relationship to man.
Let's take an atheist (John) who has 10 billion dollars. He is walking down the street and sees a 10 year old homeless girl (Jane) on the street, starving to death. Jane politely asks John if he can buy her 1 basic meal so that she will not starve to death. There are no impediments from John doing so (such as lack of time, fear of being scammed). John simply says "no, I do not have to help you, it is my money and I do not feel like helping you at the moment".
In my view John has committed a grave sin by refusing to help Jane in that situation. It does not matter that he is not Christian and that the Holy Spirit has not prompted him to help Jane.
Or let's say that John in this situation is a Christian, but for whatever (granted, unlikely) reason the Holy Spirit has not prompted him to help Jane. John still refuses. I think John has still sinned, regardless of the promptings of the Holy Spirit.