Mute that npub. I've done it since the first DM. No more issues!
Discussion
Shouldn't have to mute to get rid of it, it's why I'm looking forward to the future Amethyst update where this just appears as a popup.
It's actuallt blastr's fault for blasting to paid relays.
Reminders to pay paid relays should only "popup" for relays you manually choose. Otherwise it's an even more intrusive form of spam.
The problem is any npub can send an invoice request, and just blocking all invoices would be bad.
To me its appropriate to not show content or invoices for npubs you arent following.
Also appropriate to warn "This might be a scam or spam" if your followers have reported the same npub for such.