This will keep happening in the future and worse as billions use nostr. The problem here is relays are free so anyone can connect to it.

The solution is simple. Require users to send a "follow request" before being able to interact with a profile. This would slow down the reply bot. But then he would send thousands, millions of follow requests.

So then the solution would be to require a fee of 1 Satoshi or less to send follow requests.

Boom. Not only did that make it too expensive for the reply bot to function this would also allow the relays to stay free. This solution would cut down on spam massively.