What is the best way for non-professionals to have an opinion on questions about grammar that are not settled? I mean anyone who thinks about unsettled or live questions in grammar when there is no consensus (and are not doing new research). An obvious, and I hope pertinent, example is the Oxford comma. Another is whether punctuation is part of grammar. Or (to take a generic example from this site) is word x a y part of speech.
I'm not saying don't (you need an opinion on the Oxford comma really), I simply don't understand how.
I'm asking partly due to a wish to study the science of correct usage (not just ask questions and understand answers on ELU I mean), applied linguistics, so apologies in advance if this is a bad fit for meta.
This section is an aside to show that I am not misunderstanding what I'm asking, or what academics study.
This may be best thought of as a matter of applied linguistics, rather than pure linguistics, in the same way that physics involves applied mathematics, which physicists must work with
Google says that the difference between descriptive and prescriptive linguistics, even today, is "thin", implying that you can't get away from one and study the other. So I'm interested in learning about both.
Geoffrey Nunberg challenges a widespread assumption that the linguistic structure of written languages is qualitatively identical to that of spoken language... Analyzed in its own terms, however, punctuation manifests a coherent linguistic subsystem of “text-grammar” that coexists in writing with the system of “lexical grammar” that has been the traditional object of linguistic inquiry.
But less so its application to anything but correct usage.