) -> DiscussionExpertsResults:
    commenters = Counter()
    last_month_commenters = Counter()
    three_months_commenters = Counter()
    six_months_commenters = Counter()
    one_year_commenters = Counter()
    authors: Dict[str, Author] = {}

    now = datetime.now(tz=timezone.utc)
    one_month_ago = now - timedelta(days=30)
    three_months_ago = now - timedelta(days=90)