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Reddit also allows or used to allow commenting on the some ads.

Outrage drives engagement, it's making people engaged with ads. I'm sure there's a positive effect there to conversation rates.

Facebook/Meta also allows it I think, but comment section on ad publications is heavily moderated

Twitter also

Although, now it is also possible to disable replies on a tweet (sponsored or otherwise)

I noticed the opposite, there's a lot of people leaving positive comments on a lot of ads.

Facebook also allows that