We do not want discussions. We want questions with answers. Whether or not these are pointless, or noob stuff should be determined by voting.
As with chemistry, I don't really like too many generalisations, especially not on the fuzzy interpretation level. There certainly are questions that are too basic, which becomes too broad in terms of answering them, which would make them off-topic. Otherwise normal criteria of closing should be applied.
The question about physical and chemical change is problematic though - and you see that with the reception. I don't want to answer it here, but in very short terms, it is very opinion-based. However, the comment you linked to is noise and should probably better not have been left. The user might have instead simply down-voted and moved on.
In conclusion: I would decide these things on a case by case basis, let voting be the guiding factor. I certainly don't want to discourage curiosity. And I most certainly do not want to close such questions.