Private reply
Why it matters for creators
Private replies are the machinery behind comment-to-DM: they're what allows a tool to answer a specific comment with a DM even though the commenter never messaged you first. Without this feature, automation could only reply publicly in the thread.
The one-message limit shapes how good automations are written. That single DM has to deliver the promised thing and give the person a reason to respond (a question, a button) because once they reply, the standard 24-hour messaging window opens and a real conversation can continue.
Two ceilings govern private replies, and they sit on different axes: Meta allows 750 an hour per professional account, and exactly one per comment. The first is how many comments you can answer; the second is how many times you can answer each. Both figures, with the arithmetic and the date they were read, are in Instagram's DM limits.