1.  commentator(n = noun.person) observer - an expert who observes and comments on something;
is a kind of expert
has particulars: annotator
Derived form verb commentate₂

2.  commentator(n = noun.person) reviewer - a writer who reports and analyzes events of the day;
is a kind of author, writer
Derived form verb commentate₁

   One who writes a commentary or comments; an expositor; an annotator. [1913 Webster]
"The commentator's professed object is to explain, to enforce, to illustrate doctrines claimed as true." [1913 Webster]

commentator, n.
1 a person who provides a commentary on an event etc.
2 the writer of a commentary.
3 a person who writes or speaks on current events.

Etymology:
L f. commentari frequent. of comminisci devise

N  dissertation, treatise, essay, thesis, theme, monograph, tract, tractate, tractation, discourse, memoir, disquisition, lecture, sermon, homily, pandect, excursus, commentary, review, critique, criticism, article, leader, leading article, editorial, running commentary, investigation, study, discussion, exposition, commentator, critic, essayist, pamphleteer, discursive, discoursive, disquisitionary, expository.

N  judgment, result, conclusion, upshot, deduction, inference, ergotism, illation, corollary, porism, moral, estimation, valuation, appreciation, judication, dijudication, adjudication, arbitrament, arbitrement, arbitration, assessment, ponderation, valorization, award, estimate, review, criticism, critique, notice, report, decision, determination, judgment, finding, verdict, sentence, decree, findings of fact, findings of law, res judicata, plebiscite, voice, casting vote, vote, opinion, good judgment, judge, umpire, arbiter, arbitrator, asessor, referee, censor, reviewer, critic, connoisseur, commentator, inspector, inspecting officer, twenty-twenty hindsight, armchair general, monday morning quarterback, judging, judicious, determinate, conclusive, on the whole, all things considered, a Daniel come to judgment, and stand a critic, hated yet caress'd, it is much easier to be critical than to be correc, la critique est aisee et l'art est difficile, nothing if not critical, O most lame and impotent conclusion.

N  interpreter, expositor, expounder, exponent, explainer, demonstrator, scholiast, commentator, annotator, metaphrast, paraphrast, glossarist, prolocutor, spokesman, speaker, mouthpiece, dragoman, courier, valet de place, cicerone, showman, oneirocritic, (Edipus, oracle).

sports commentator