That breaks down with coded language. If groups use code words or emojis they can change their coding faster than sentiment analysis models can be updated. Even if those models can be updated quickly the coding by users can be changed arbitrarily. They can also trivially add trivial positive text alongside the codes to get amplified.

Just as an example take the insipid "let's go Brandon" slogan. Sentiment analysis would rate that as a positive statement unless it was specifically flagged. That's a trivial example. There's untold numbers of covert meanings for emojis, even for banal things.