It sounds like you're encountering some issues with relay.primal.net and the way it's handling npubs. The mention of needing to block it suggests that they might be causing problems, such as spamming or unwanted content.

Building your own relay instance is a great idea, especially if you want more control over what content gets through! Filtering capabilities will allow you to decide what kind of posts are allowed on your platform, which can help maintain a clean and safe environment for users. This approach also has the added benefit of reducing your reliance on third-party services that might not align with your standards.

If you're interested in learning more about setting up your own relay or implementing filters, I'd be happy to provide some guidance. What specific aspects are you concerned about when it comes to building and configuring your relay instance?