Em dashes on Reddit have become ten times more popular in a few years. The Ukrainian team KissMyPost studied how writing has changed since the advent of AI

The share of posts with em dashes has increased more than ninefold

KissMyPost, a Ukrainian team working with Reddit analytics, has published a study on how the use of the em dash in posts and comments on the platform has changed over the past decade. The researchers examined 15,817,377 text posts and over 241.5 million comments in 100 large English-language Reddit communities. They took into account texts of at least 200 characters in length, and for posts, also titles. The analysis covers the period from January 2016 to September 2026.

At the beginning of 2021, the em dash (—) symbol was present in about 0,70% of long posts in the sample. By the second quarter of 2025, the share had increased to 6,53%, a more than ninefold increase. On a monthly chart, the figure peaked in July 2025 at 6,83%.

The researchers tracked not only posts but also comments. There, the change was much smaller: the share of long comments with this sign increased from 0,65% in the second quarter of 2024 to 1,32% in the second quarter of 2025.

This distinction is important for interpreting the results. Comments are typically written directly in the Reddit window, while posts are more likely to be prepared elsewhere and then posted to the platform. The study authors suggest that the proliferation of AI-generated or edited texts may have influenced the trend. However, the data alone do not allow us to definitively determine the cause.

In August 2025, the figure fell by 17%

The most noticeable change occurred after the peak in the summer of 2025. In August, the share of long posts with an em dash decreased from 6,83% to 5,70% — a 17% drop in one month.

This coincided with ChatGPT’s transition to GPT-5 as the default model on August 7, 2025. According to KissMyPost, 63 of 74 subreddits that had enough posts in July for comparison saw a decrease in the proportion of em dash posts in August. However, the authors do not claim that the launch of GPT-5 caused the drop. The timing may be indicative, but it does not prove causation. Other factors may have influenced punctuation usage. The rate also did not return to its level at the beginning of the decade. In December 2025, it fell to 4,78%, and in September 2026 it was 5,61% — about seven times the average level in 2021.

Can you recognize ChatGPT text by dashes?

The em dash has become one of the most popular markers that users use to identify AI-generated text. But KissMyPost cautions against jumping to conclusions: the symbol was in use long before ChatGPT, and its prevalence varies significantly across communities. The researchers also tested an alternative explanation: automatic character substitution by smartphone keyboards. A similar shift had already occurred after the release of iOS 11 in 2017, when the em dash appeared more often in both posts and comments. In 2024–2025, the picture was different: posts changed much more than comments, and the use of double hyphens did not show a similar shift.

This is consistent with the hypothesis that people are increasingly pasting into Reddit text written in other applications, including those using AI. But this is still speculation, not proof of the origin of each post.

“The em dash is not a marker that allows us to determine the authorship of a particular text,” is the main conclusion of the study. Even if the symbol has become statistically much more common, it does not reliably say anything about who wrote a particular publication.

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