This isn’t speculation. We looked at the data.

Across 66 million comments in 2,147 subreddits, we scored every comment for relevance to its parent post using zerank-2, then compared the reranker’s ordering to Reddit’s native karma ordering. The “best answer” in the numbers below is the comment zerank-2 ranks first — a defensible proxy for substantive relevance, not a human-labeled gold standard. On most threads, that comment is not the one at the top.

The sorting is broken. Karma rewards speed, social proof, and tone-matching. It does not reward being correct, being thorough, or being relevant.

So we built a tool that does.

Reddit Reranker

Reddit Reranker is a Chrome extension that re-sorts comments on Reddit and Hacker News using zerank-2, ZeroEntropy’s reranker. It reads the comments on the page, scores each one for relevance to the post, and reorders them. One click.

It works on:

• old.reddit.com — the classic interface
• www.reddit.com — new Reddit
• news.ycombinator.com — Hacker News

Install it, paste your API key, and click Rerank. That’s it.

How It Works

The extension extracts every comment on the page and sends them to zerank-2 as documents, with the post title and body as the query. zerank-2 returns a relevance score for each comment — not “how popular is this,” but “how relevant is this to the post.”

Top-level comments get reordered by score. Threaded replies stay grouped with their parent, so conversation structure is preserved. Every comment gets a color-coded relevance badge (yellow to blue) so you can see the scores at a glance.

The whole operation takes 1–3 seconds on a typical thread.

Six Ways to Read a Thread

Not every rerank should optimize for the same thing. Sometimes you want the most informed reply; sometimes you want the jokes; sometimes you want to see what’s controversial.

Reddit Reranker ships with six scoring modes:

Mode	What it surfaces
Relevant	Best overall responses to the post
Informed	Expert replies with sources, citations, depth
Joke	Humor, sarcasm, memes, meta-commentary
Inflammatory	Controversial, combative, polarizing takes
Actionable	Practical advice, step-by-step instructions
Custom	Your own natural-language query — score by whatever you want

Each mode steers zerank-2’s notion of relevance by prepending an instruction to the query. This is the same instruction-following capability that makes zerank-2 useful in production RAG pipelines — applied here to a Reddit thread. For the mechanics of writing instructions that reliably shift a reranker’s behaviour, see prompting best practices for instruction-following rerankers.

Karma vs. Relevance: The Stats Panel

After reranking, the extension shows a statistics overlay with a scatter plot of karma vs. relevance score for every comment in the thread. The x-axis is log-scaled karma; the y-axis is the zerank-2 relevance score. A trend line and Pearson correlation coefficient (r) are computed on the fly.

Across the 2,147-subreddit study, the median Pearson correlation between log-karma and zerank-2 relevance was r = — weakly positive on average, often near zero, and occasionally negative on threads where the top-karma reply is a one-line joke. High-karma comments are not reliably the most relevant. This is the whole point.

The panel also shows a histogram of relevance score distribution, mean and median scores, and a breakdown of high-confidence (≥ 70%) vs. low-confidence (< 30%) comments.

Why This Matters Beyond Reddit

Reddit Reranker is a consumer demonstration of what zerank-2 does in production. The same model that re-sorts these comments is used by enterprise teams to rerank search results, filter RAG context windows, and score document relevance across legal, medical, financial, and technical domains.

If you’ve been evaluating rerankers for your own pipeline, this is a way to see zerank-2 work on messy, real-world, adversarial text — not curated benchmark data. Reddit comments are noisy, sarcastic, off-topic, and full of context that only humans would catch. It’s a good stress test.

Get It