A social advertisement carries its own comment thread, visible to everyone who sees it. That thread becomes part of the advertisement, and it affects what the placement costs.
Comments are read as social proof
People encountering an unfamiliar brand use the visible reaction of others to decide whether to take it seriously. A thread of specific, positive replies performs that function efficiently.
A thread of complaints performs the opposite function with equal efficiency, and it does so before the viewer has engaged with the message at all.
The advertisement and the reaction to it are therefore consumed together, which is not true of most other media where audience response is invisible.
Reactions feed the delivery model
Platforms interpret engagement signals when predicting how future viewers will respond. Negative interactions push the prediction down.
A lower predicted quality score reduces ranking in the auction, and the advertiser must bid more to win the same impressions.
The cost increase is therefore not a penalty applied deliberately. It is the ordinary result of a system that expects the next viewer to react like the last ones.
Unanswered questions are lost conversions
A large share of comments are practical enquiries about availability, delivery or specification, left by people considering a purchase.
These accumulate under advertisements that no one is monitoring, and each unanswered one is a person who moved on rather than a person who complained.
Response time matters because the thread is being read live. An answer arriving days later is documentation rather than a sale.
Threads persist across the campaign
Where an advertisement is built on a single post identifier reused across campaigns, the comments accumulate rather than resetting each time.
This is an advantage for an advertisement with a healthy thread and a serious liability for one that attracted a hostile response early.
Duplicating the creative into a fresh post clears the history, at the cost of also clearing the accumulated proof that made the original work.
Moderation is a trade with visible costs
Hiding critical comments is possible and is often noticed, particularly where the criticism concerns a genuine service problem.
Removing abuse and off-topic material is uncontroversial, but removing substantive complaints tends to generate more of them once the practice becomes apparent.
The more durable approach is to answer directly in the thread, since a visible, specific reply reassures the far larger group of readers who never comment at all.