the.com/commenter

means A person who posts a written reaction to something, usually online, adding their take to the public record of a piece or thread.

from Built from 'comment,' which traces back to Latin 'commentum' (an invented thing, a contrivance) and 'comminisci' (to devise, to think up), via medieval Latin 'commentarius' meaning a notebook or set of annotations. The '-er' just tacks on the doer. So etymologically, a commenter is someone who 'devises' a note on the margins of someone else's work — the Latin root already had a faint whiff of fabrication baked in, centuries before the internet gave it room to run.