Why LLMs Have a 'Reddit Voice': Three Eras of Training Data
ethayarajh · x · 2026-07-31
Large Language Models (LLMs) often exhibit a distinct 'Reddit tone,' which is deeply tied to the evolution of their training data. The use of Reddit in model training can be broken down into three eras:
- Reddit as Filter (2019): During the GPT-2 era, OpenAI used outbound links from Reddit posts with a karma score of at least 3 to scrape high-quality web pages, forming the WebText dataset.
- 'Narrow' Reddit (2019-2023): Specific subreddits like /r/ELI5 and /r/TL;DR were mined to train models on narrow tasks like QA and summarization. The canonical RLHF paper notably used /r/TL;DR to train its reward model.
- 'Broad' Reddit (2023-onwards): Stanford NLP released the SHP dataset, comprising 385k pairwise human preferences across 18 subreddits, further deeply embedding Reddit's community style into the model alignment process.
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