It's the maximum value of a signed 16 bit integer. But there's a GitHub page that explains hn lore.

What HN-lore page are you referring to? This[0] one explicitly states:

> Although submissions cannot be downvoted, [...]

	▲	tnelsond4 39 minutes ago \| parent [-]
		I meant to reply to John who was asking where someone was getting the 32768 number from. No idea if it's true, but that's the significance of that number. Yeah that's the lore page does look like there's no downvoting submissions then and people are just trolling.