Text generation is now cheap, so I expect this problem to worsen. I hate to write it, but I don't see any other solution on platforms, that aspire to be a modern agora, than identity verification ...
Why would identity verification solve this? The spammer can just verify himself, or if he doesn't want to or it's at a bigger scale than individual, then there will be services where you can get identity verifications on the cheap and they'll work either by paying people in a poor country to verify themselves all day, or, even more cheaply, sketchy age verification services on sketchy porn sites will be actually proxying or replaying people's verifications to another service of your choice
Why would identity verification solve this? The spammer can just verify himself, or if he doesn't want to or it's at a bigger scale than individual, then there will be services where you can get identity verifications on the cheap and they'll work either by paying people in a poor country to verify themselves all day, or, even more cheaply, sketchy age verification services on sketchy porn sites will be actually proxying or replaying people's verifications to another service of your choice