In spite of every programmer at work following the same styling guidelines and programming patterns, I can quite easily identify the author of a pull request by reading their code alone. The commenter's claim seems plausible to me.

I might actually have an easier time identifying authors by commit messages/patterns rather than their content since the styling guidelines are mostly handled by linters.

Someone created a tool two years ago that does this, https://stylometry.net but it appears to be offline. The creator at the time said:

This site lets you put in a username and get the users with the most similar writing style to that user. It confirmed several users who I suspected were alts and after informally asking around has identified abandoned accounts of people I know from many years ago. I made this site mostly to show how easy this is and how it can erode online privacy. If some guy with a little bit of Python, and $8 to rent a decent dedicated server for a day can make this, imagine what a company with millions of dollars and a couple dozen PhD linguists could do.

https://news.ycombinator.com/item?id=33755016

It's also possible to eyeball similar writing styles, although not at scale. That's how "Fake Steve Jobs" was uncovered in 2007:

Last year, his agent showed the manuscript to several book publishers and told them the anonymous author was a published novelist and writer for a major business magazine. The New York Times found Mr. Lyons by looking for writers who fit those two criteria, and then by comparing the writing of “Fake Steve” to a blog Mr. Lyons writes in his own name, called Floating Point

https://www.nytimes.com/2007/08/06/technology/06steve.html#:....