And scammers will create AI chatbots to try and scam people, we’ll end up with a lot of computing power and bandwith lost for endless conversations, everything is fine

Here is the story OP might be thinking of https://www.laquadrature.net/en/2023/10/06/the-beginning-of-the-8-december-trial-is-also-the-judgement-of-the-right-to-privacy-and-encryption/

So nobody was arrested for using signal, however it was considered as incriminating evidence during the trial that they protected their privacy and didnt want to give their im encryption keys to law enforcement