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You're commenting on Hacker News, a news forum run by Y Combinator. I think it's fair to assume the broad HN community knows that YC = Y Combinator, and from there that S20 means Summer 2020, and that batch means the set of startups funded by ycombinator. In that context remote should make sense, but the link explains that part.

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https://news.ycombinator.com/newsguidelines.html

YC S20 Remote Batch = YCombinator Summer 2020 Batch, remote. It's the same styling they've used for as long as I can recall. W21 will be the Winter 2021 batch, W20 was the W 2020 batch.

Summer 2020. A lot of people who read HN are probably familiar with the style, so they seemed to have omitted a longform of the abbreviation. Other pages on the linked site call it "Summer 2020", "Winter 2020", etc.