> Its name is an anagram of Scott Alexander, Slate Star Codex, and Astral Codex Ten

That would be difficult, since those three phrases are not anagrams of each other.

Where is the 'n' in 'data secrets lox'?

It's an anagram of "Slate Star Codex" but not of the others.

It's the forum that frequent commenters on Slate Star Codex set up to chat while Slate Star Codex was on its NYT-induced hiatus. It seems to have developed a life of its own and is still in use even now that Slate Star Codex is back as Astral Codex Ten.