I don't like it either (wish we could discuss them). But it's a special, deliberate perk of YC job posts. From the FAQ (
https://news.ycombinator.com/newsfaq.html):
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Can I post a job ad?
[...]
Another kind of job ad is reserved for YC-funded startups. These appear on the front page, but are not stories: they have no vote arrows, points, or comments. They begin part-way down and fall steadily. Only one is on the front page at a time. The rest are listed at jobs.
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What's the relationship between YC and HN?
Y Combinator owns and funds HN. The HN team is editorially independent.
HN gives three features to YC: job ads (see above) and startup launches get placed on the front page, and YC founder names are displayed to other YC alumni in orange.