[gucci-on-fleek]

HN is different from other platforms in two key ways: the moderators here are paid and work full-time on the site, and there's only a single community here, without any subforums or similar. I can't think of any other platforms with both of these in common.

HN is also different from Reddit/Digg because it only allows text and links, but this is the same as Usenet and most old-school forums. And then there are some intangible cultural differences, but every platform thinks that they're special, so there's nothing really unique here.