No - I meant I will check if Mattn-san is showing as Spammer for me after unfollowing.

But you're not shown as spammer for me -

Amethyst marks people with 5 or more repeated posts as spam, but has exceptions for short messages and bot calling. The only 2 possibilities I see are

1. Mattn-san posted a long message multiple times but that got published in Japanese relays only (I read only from yabume, if there are repeated posts on other relays I won't know)

2. 5 of Yonle-san's follows have reported Mattn-san as spam, but again those reports are only on Japanese relays, as I can see any reports(this is extremely unlikely scenario)

I'd suggest Yonle-san to write a post marking Vitor-san, so that we can know exact post that's leading to this.