I recently added “Your LLM was trained on my blog” to the intro on my home page. I’m sort of being facetious, but it’s also true: my old site (hyperborea.org) has been in the Common Crawl data set for years, this blog has been online since 2002, and the major LLMs have used Common Crawl’s data in their training.

Way back when I switched to WordPress in 2003, one of the things I found annoying about it was that it would auto-convert punctuation from ASCII to “fancy” characters. Curly quotes, curly apostrophes, em-dashes instead of double-hyphens, ellipses…These were things that bugged the heck out of me when I saw them in broken emails and Word documents. Over the next year, seeing the difference it made in legibility, I came to appreciate real typography. Since then I’ve been happy to let WordPress, and later ClassicPress and Eleventy convert my plain typing.

Side note: I still have trouble using some apps with code snippets (ex: Apple Notes and Stickies), ’cause I haven’t figured out how to stop them from converting ASCII punctuation that means something in the code to Unicode punctuation that means something more specific in printed human language. Also, notice in that sentence that ClassicPress was smart enough to convert a straight up and down apostrophe used on a contraction to a curly apostrophe, and not to a curly single quote like it does with ‘here.’

Anyway, WordPress powers a huge amount of the web. I’ve seen stats bandied about such as 42% of all websites, 60% of content management systems, >50% of the top 10,000 websites (by some measure or another). The exact numbers aren’t important, it’s just important to know that a whole lot of the web uses WordPress to convert what people write into HTML pages for the web.

Now let’s get back to LLMs:

• People think they can identify LLM-generated text because it tends to include em-dashes.
• LLMs were trained on writing by actual people on the web.
• A whole lot of that writing by actual people is presented by WordPress.
• WordPress has auto-converted typography including em-dashes since 2003.
• That means a large chunk of LLMs’ training data includes text by real people that uses real em-dashes.

“AI” doesn’t use em-dashes because real people don’t, it uses em-dashes because real people do [note: lots of swearing] (via).

The only place I can imagine it would be even a semi-reliable indicator would be in social media posts, on platforms where that kind of auto-conversion doesn’t happen. Even then, I can easily imagine someone writing a draft in Word, or copying a sentence or two from their WordPress post, or just hitting option+shift+hyphen on a Mac (or whatever the key combo is on Windows).