system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do newspapers or news put brackets around words or letters in a quote from someone?
gpt
Usually to provide context for a quote that originally used pronouns.  If the quoted person actually said, "He does not know what he's talking about," but the newspaper wants to make clear who the subject of that sentence was, they would write, "[Barack Obama] does not know what he's talking about." 

It can also be used to properly capitalize a quote that begins in the middle of a sentence.  If the quoted person said, "This movie is terrible because the acting is so bad," but the newspaper wants to truncate that quote, they could write, "[T]he acting is so bad."