Reputation matters. On some Japanese BBSes, spammers tend to use non-Japanese IPs or data center IPs. A good chunk of the spam goes away by blocking non-Japan

Reputation matters. On some Japanese BBSes, spammers tend to use non-Japanese IPs or data center IPs. A good chunk of the spam goes away by blocking non-Japan IPs (easy to do with BGP data) and disallowing data center IPs (these often host VPNs, scrapers, etc.) from posting. Posting from overseas thus costs money or is not possible. The trade-off is 1-100 extra users or significantly reduced spam for little effort. It's not surprising that most website operators choose the latter. I also know of a file uploader that recently had to block overseas IPs due to such IPs repeatedly uploading illegal content. This is an example of a few bad actors ruining things for everyone.