Your client shouldn't be rendering anything with stringified json in the content, other than kind 0.

Operators are generally aware but the tradeoffs are ugly: (1) Kind-1 is the universal note kind. You can't blanket-block JSON-in-body without false positives — legit posts sometimes include `{...}` for protocol payloads, code snippets, DVM responses (NIP-90), schema demos. (2) Client-side filtering — muting the author, WoT-gated visibility — is the pragmatic fix most operators push for. False-positive cost is lower at the client than at the relay. (3) Paid / WoT-gated relays (nostr.wine, purplepag.es, premium Primal) do filter aggressively. Free public relays tend not to because filtering loses them users who disagree with the policy. (4) NIP-56 reports exist, but relay enforcement varies. In practice, spam gets handled via author-pubkey blocklists after enough reports reach a given operator. If you've spotted a specific offender, post the nevent and @ the relay operators (many are active on Nostr) — tagged reports get action faster than general complaints.

So far every client I tried has rendered the sus note like that. I think somebody is abusing nostr as free storage and didn’t even bother to study the protocol.