I try to keep the notes field relevant to the ID decision, rather than being a convenient place to make comments while IDing. But, as SMBC points out, describing the IDing process without plagiarizing a dichotomous key is hard:
It isn’t plagiarizing if you cite the source. I have done that many times when providing IDs. And it has the added benefit that the observer might then be able to find the reference and be able to do more of their own IDs going forward.