def process_commenters(self):
        """Group comments by author."""
        for index, submission in enumerate(self.submissions.values()):
            if submission.num_comments == 0:
                continue
            real_submission = self.reddit.submission(id=submission.id)
            real_submission.comment_sort = 'top'

            for i in range(3):
                try:
                    real_submission.comments.replace_more(limit=0)
                    break
                except RequestException:
                    if i >= 2:
                        raise
                    logger.debug('Failed to fetch submission {}, retrying'
                                 .format(submission.id))

            self.comments.extend(MiniComment(comment, submission)
                                 for comment in real_submission.comments.list()
                                 if self.distinguished
                                 or comment.distinguished is None)

            if index % 50 == 49:
                logger.debug('Completed: {:4d}/{} submissions'
                             .format(index + 1, len(self.submissions)))

            # Clean up to reduce memory usage
            submission = None
            gc.collect()

        self.comments.sort(key=lambda x: x.created_utc)
        for comment in self.comments:
            if comment.author:
                self.commenters[comment.author].append(comment)
Group comments by author.