Comment-to-DM describes taking a conversation that began as a public comment on a Facebook or Instagram ad and continuing it as a private message. On Meta's platforms this is done through a private reply — a message a Page can send privately in response to a comment, within the policy window Meta defines for it.
It is a natural fit for buyer-intent comments. When someone comments "is this still available?" under your ad, a private reply lets you answer with details — pricing, links, stock — without conducting the whole sale in public, while still acknowledging the public comment so others see you are responsive.
The important constraints are honesty and policy. Private replies are only permitted within Meta's rules and timing window, and they should never feel like spam. ROAS Shield treats comment-to-DM the same way it treats public replies: it can draft a private reply for a buyer-intent comment, but replies are draft-only by default, so a human approves before anything is sent. Auto-send is only available once you opt in and the model's confidence and safety checks pass.
For the wider conversion picture, see how to turn ad comments into customers, and for the public-reply version, how to reply to Facebook ad comments.