openide/plugins/github/resources/graphql/query/addReviewComment.graphql

mutation ($reviewId: ID!, $body: String!, $commit: GitObjectID, $file: String, $position: Int, $inReplyTo: ID) {
  addPullRequestReviewComment(input: {pullRequestReviewId: $reviewId, body: $body, commitOID: $commit, path: $file, position: $position, inReplyTo: $inReplyTo}) {
    comment {
      ...pullRequestReviewComment
    }
  }
}