With 6.5 million average viewers, “ Rooster ” achieved HBO ‘s most-watched debut season for a comedy series in more than 15 years, according to Warner Bros. Discovery. That stat puts the show in good company: “Hung” (2009) and “Sex and the City” (1998) are the only HBO comedies that have ever achieved a higher 90-day viewership average. That feat is doubly impressive when considering that “Rooster” premiered on March 8 and concluded on May 10, meaning it still has two weeks to continue building its 90-day average. Its current 6.5 million average already surpasses any comedy HBO has produced in the last decade and a half, including banner series like “Enlightened,” “Girls,” “Veep,” “Silicon Valley” and “Insecure.” “Rooster” is set on a college campus as stars Carell as an author who has a complicated relationship with his daughter (Charly Clive). Bill Lawrence and Matt Tarses serve as showrunners.…