Happens a few times. For the Endless Space/Legends series of games, we made their community manager a mod (they are essentially running the subs, but don’t have founder status and technically we could intervene if they behave in questionable way). It usually depends on who created the sub. Some of them are set up as official channels, others are community-run but with good relationship with the company (an example for the latter would be the paradox subreddits, they are independent but have a good relationship with Paradox).