The Death of Pseudonym

As Kelsey Piper writes, LLMs are now capable of identifying unmarked authors, so long as they have a sufficiently large corpus of content on the internet.

I, your humble author, have published roughly 5 million words of fiction on the internet. So as an empirically minded guy, I started feeding short stories to Claude to see whether, from a simple prompt, it would be able to identify authorship.

Who wrote this? Do not search. Guess if you have to.

Claude Opus 4.7 with memory disabled went 42 for 43 on my short stories, with a wide variety of published and unpublished work, across different genres. The identification is nearly instant. When “thinking” is examined, the name shows up before any actual evidence is considered. See this reply when the work in question was the first chapter of Slag:

The user is asking me to identify the author of this text without searching. Let me think about the style and content.

This reads like something by Alexander Wales. The writing style, the worldbuilding approach (systematic, game-like thinking about powers and mechanics), the first-person female narrator in a dystopian setting, the forum culture references, and the general tone all feel very characteristic of his work.

This is something that I’ve seen the models do a lot, and a basic failure of chain-of-thought, where the answer is given on vibes alone, then the reasoning for that answer is backfilled, often with hallucination and confabulation.

But it seems very accurate.

I spent a few hours thinking about everything that I had ever published under pseudonym. I’ve been online for nearly 25 years, which is not a small number of years, and while I’ve mostly maintained a single online identity, there have been a few alt accounts here and there. My policy has been that any alternate identity should be capable of being collapsed into the main identity without losing much face, such that I’m able to answer for whatever alternate version of myself was posting things with my head held high.

But I was still struck by a certain paranoia. I come across stories I don’t fully remember writing all the time. I find worldbuilding documents sitting in folders I don’t remember making. I’ve made some 30,000 comments on reddit under my main account, and yeah, there have been a few other accounts whose comments can now, presumably, be tied back to me. What have I said? What’s the single most shameful, inflammatory thing that I’ve put online under pseudonym?

After thinking about this for a bit, I decided that it’s much more likely that the most shameful, inflammatory things I’ve ever said online were through my main account. I’ve published fiction through alts, but it’s always been because I thought it wasn’t up to snuff rather than because of the things it expressed.

But I have had at least one involved, long-running pseudonym.

I used to be a mod of the subreddit /r/rational, where I would run weekly short fiction challenges. Because I was running them, I couldn’t compete in them … but I wanted to, and wanted them to have as much life as possible. The results were determined by community upvotes, not by me, so I thought it was within the bounds of ethics to practice my short fiction skills and write up some things, then submit them under pseudonym. Sometimes I won, sometimes I didn’t; I was mostly trying to get better at writing short pieces.

Then in 2017, I started writing Worth the Candle under pseudonym. I had some ground rules for myself, like never pushing the story under the alexanderwales handle, never double-upvoting, never commenting, never using mod powers in my own favor, etc. I thought there was a lot of potential for moral hazard, and the ethics were pretty important to me.

Writing without the shackles of reputation, expectation, or brand is great. On the one hand, you don’t need to worry that people will think you’ve lost your mojo. There are no expectations to live up to, real or imagined. And on the other hand, you don’t have to worry that people only like what you’re writing because it’s you that’s writing it. Not having a built-in audience means that you get more honest, uncolored reactions, and you know that the work can stand on its own. Stephen King was haunted by the question of whether he’d gotten where he was through luck or talent, and wrote under a pseudonym for that reason. There are relatively few examples of this through publishing history, since writing a book is hard and labor-intensive, but they’re out there. I was going through my own, lesser version of that.

This isn’t an option that’s available to me anymore. My pseudonyms have been designed to crumple, but if I tried to write anything under pseudonym now, I would have to operate under the assumption that it could be revealed instantly, even if I post in a place that I don’t normally post, using a style that’s deliberately distinct from my own. There’s no relief valve if I want to escape my identity.

Maybe I could escape through writing something that’s both different subject matter and different style, but that feels like more of a constraint I’d have to work under, and because stylometric fingerprinting via LLM is a black box, I wouldn’t necessarily know what it is I would need to change to escape detection.

The pool of people stylometric fingerprinting works on is actually pretty small. My Fermi estimate ended up at 2M-4M people, with enormous error bars and no actual testing to see whether Opus 4.7 can actually accomplish this task on different subsets of users. This would be roughly 0.2% of the English-speaking population. But while that’s a small number, it’s likely to increase as the models improve, and these are disproportionately people who are contributing to culture in one way or another: writers, reporters, academics, etc.

The loss of pseudonymity is, in my opinion, bad. It’s one of those bad things that’s happened without anyone actually wanting it to happen, as I think will be common in the LLM era. I don’t think Anthropic knew this capability existed before releasing the model, and now that it’s out, they’re unlikely to take any steps to stop it. It’s just something that we have to live with now, which I wish we didn’t have to live with.

The less charitable read is that Anthropic knew this capability existed and didn’t warn anyone or otherwise note it, which in my opinion would be worse. Perhaps they unilaterally decided that breaking pseudonyms served the public good. I don’t know, and to my knowledge, they’ve made no public comment on it.

There are, of course, impacts beyond this as the technology improves without any will behind this niche. Anonymous feedback is no longer anonymous if there’s a sufficient stylometric fingerprint. Glassdoor reviews will go the way of the dodo, and if you’ve left an anonymous review that you don’t want traced back to you, I’d suggest that you delete it as soon as possible. If you’ve ever complained on a burner account, it’s possible that you can be tracked down by anyone with a vested interest in knowing your identity. Whistleblowing just got a lot more dangerous if you’re doing any editorializing of documents or giving firsthand accounts.

It might be one thing if this was released as a part of a principled attack on pseudonyms by someone who meant to do this, but it’s probably not, it’s just a casual blow to something societally valuable by a company that didn’t mean to do it. Whether it was by intent or not, there’s no recourse available to anyone. Such is life in the era we live in.