Opus 4.7 knows the real Kelsey

Perceived new capability: automated stylometry

• Many commenters report that the model can correctly guess the author of short text samples, including:
  • Unpublished blog drafts and book excerpts.
  • Private or semi-private community posts.
  • Posts written after the model’s stated training cutoff.
• Others see clear limits: mislabeling ordinary posts as coming from a few prolific writers, or only narrowing to a “type” of tech/rationalist blogger.

Memory vs training vs genuine inference

• Multiple people stress that memory and account linkage were disabled or controlled (incognito, API, different users), yet the model still identified authors.
• Some speculate earlier testing texts may have entered later training.
• Several note that explanations for “how” the model recognized an author felt post‑hoc and implausible; the model likely can’t introspect its real mechanism.

Privacy and deanonymization concerns

• Strong theme: this looks like the beginning of routine deanonymization from writing style, especially for anyone with a sizable public corpus.
• Commenters fear:
  • Linking pseudonymous posts or private emails to real identities.
  • Outing vulnerable groups or political minorities at scale.
  • Future models using personal AI chat logs to answer questions about individuals.
• Some argue effective online anonymity may never have truly existed, given infrastructure-level tracking.

Defenses and trade‑offs

• Proposed defenses:
  • Run all writing through a local or separate LLM to “de-style” it.
  • Intentionally write in a non‑native language or distorted style.
  • Use stylometric encoders/decoders with trusted contacts.
• Many find these options distasteful or harmful to authentic human voice and discourse.

Broader social and ethical implications

• Some imagine a near‑zero‑privacy world: potentially safer (less hidden crime) but also more oppressive and dull.
• Several tie anonymity to protection for unpopular or stigmatized groups; others push back on how such examples are framed but not on the core privacy risk.
• There is both awe at the technical feat and alarm at its implications; uncertainty remains on how widespread and reliable this ability really is beyond heavily published authors.