Movies
You know, I’d think you were acting, but you’ve never been this good.
— Rose Schwartz · Soapdish

Behind the line May contain spoilers.
Our reading
An editorial interpretation.
The speaker suggests that this could be acting, then rejects that possibility by insulting the listener's usual ability. The remark combines apparent belief with a cutting judgment of past performances. Its backhanded structure makes the compliment and the criticism arrive together in the same sentence.
Context reviewed