If a Reel blew up and you got roughly 15,000 comments in a few hours but your comment-to-DM tool only sent around 3,000 messages, nothing is broken. This is Meta's plumbing showing through, not ManyChat doing something weird. Here is exactly what is going on, point by point.
1. The rate limit and the queue
Comment private replies are capped per account on Meta's side. The documented ceiling is 750 per hour per account, and most tools deliberately throttle under that to stay ban-safe. When a spike pushes you past the cap, the excess is not dropped at the rate-limit layer. It sits in a queue and goes out as the rolling hour frees up. That is why a 15,000-comment burst trickles out over the following hours instead of landing all at once.
2. Are people getting silently skipped?
A send that fails on a genuine rate-limit error is generally retried, not silently thrown away. So the rate limit itself is usually not what loses people. The thing that actually strands commenters is the next point, and it is the one almost everyone gets wrong.
3. The window is 7 days, not 24 hours
The initial private reply to a comment has a 7-day window on Meta's side, not 24 hours. The 24-hour window you have probably read about is for continuing a conversation after someone replies to you. For the first comment-to-DM, you have a full week.
That is good news, you have far more runway than you thought. The catch: at 15,000 comments in 3 hours, even a 7-day queue running at a few hundred per hour may not clear the entire tail, and anyone who falls more than 7 days past their original comment becomes unreachable by private reply.
4. Best practices for viral-level volume
The honest starting point is that you cannot instantly DM everyone on a real spike. That is a Meta ceiling no tool escapes. What actually helps:
- Keep the first DM short and conversational. Put the link in message two. First messages that lead with a link get filtered into hidden message requests far more often, so a simple opener lands with more people.
- Go back and sweep the post. Re-scan the existing comments and DM the ones who matched your keyword but never got a message, while they are still inside the 7-day window. This is where most of your "lost" people are actually recoverable.
The short version
The cap is real and shared by every comment-to-DM tool on the market. But your misses mostly are not permanent. If you sweep the post again within 7 days, you can recover the tail that the live queue could not keep up with.
One thing worth knowing
ManyChat is forward-only. By their own docs it cannot go back and sweep a post for commenters it missed, so the overflow from a spike just slips away. We built ChatGenius to do that exact thing, a feature we call Rewind: after a post pops off, you point it at the post and it re-scans every comment and sends the DM to everyone who matched but never got one, as long as they are still in the 7-day window. It also protects your real sends under load by deferring DMs instead of dropping them.
See how Rewind works Built and run by a small founder team, so when you have a high-volume question you get a real answer. Start free.Frequently asked questions
Meta caps comment private replies per account per hour (the documented ceiling is 750 per hour, and most tools throttle under that to stay ban-safe). On a 15,000-comment spike you blow past that limit, so the excess queues and goes out as the rolling hour frees up rather than being dropped.
Yes, and it is a Meta platform limit, not a ManyChat-specific one. Every comment-to-DM tool shares the same per-account hourly ceiling, so none of them can instantly DM everyone on a true viral spike.
The initial private reply to a comment has a 7-day window. The 24-hour window applies to continuing a conversation after someone replies to you, which is a different thing. You have a full week to land the first DM.
Yes, as long as they are still inside the 7-day private-reply window. You re-scan the post and send the DM to anyone who matched but never received one. ManyChat is forward-only and cannot do this, but tools with a retroactive backfill can sweep the post and catch the tail.
Accept you cannot instant-DM everyone, keep the first DM a short conversational opener with the link in message two, and re-scan the post to recover missed commenters while you are still inside the 7-day window.