To draw out a hypothesis: existing accounts with real names and projects may value their reputation enough to not spam. Perhaps a reasonable line of thinking is

To draw out a hypothesis: existing accounts with real names and projects may value their reputation enough to not spam. Perhaps a reasonable line of thinking is spam accounts are newly created “anonymous” accounts. I haven’t looked, so I don’t know if there is any correlation. It’s an imperfect filter for spammers since of course anonymous accounts already exist.