noun
annotator; commentator
A person who adds explanatory notes or comments to a text, such as a literary work, legal document, or academic paper.
彼は古典文学の注解者として有名だ。
He is famous as an annotator of classical literature.
Compound of 注解 (annotation, comment) + 者 (person). The exact historical derivation is uncertain, but the word follows a common Sino-Japanese pattern for agent nouns.