Here's the answer: that little phrase is a capture machine. When a video says "comment GLOW and I'll send you the routine," an automation catches the keyword, delivers the promised thing instantly by DM, and then offers something more, usually the full guide in exchange for an email address. The person gets what they wanted in seconds. The creator gets a contact they own, captured at the exact moment interest peaked. And every keyword comment also boosts the post's conversation signal, so the automation literally feeds the algorithm while it collects.
This matters because of a truth most people never hear: reels rent reach, DMs own it. Instagram's public board auditions your reels to cold audiences on watch time and shares. But the private board, the DMs, the daily stories, the broadcast channels that land like a text message, is where strangers become people who know you, and where a follower becomes an email subscriber no algorithm can take away. A winning reel without a capture flow is a room full of raised hands nobody counted.
The trust rules matter as much as the mechanics: automated replies should read as service, not deception, every flow needs a path to a real human, and anything involving money or a complaint gets answered by a person. Automation buys back the hours. The hours go into relationships that can't be faked.
The full build is Volume 2 of our Social Media Bible.
Reels rent reach. DMs own it.