Alicornutopia

Yes: 5f5, 8e
No: 107 (repeated), 122, 220, 5fc, 8ef8, 8ef, 8f5, 8fc

This could go on for a while, so I will tell you that you already have enough information to guess the correct answer. In particular, remember that there are no secret random strings.

EDIT: Oops, I forgot this:

I have looked at the strings-of-which-everything-is-a-substring and I see no patterns.

All of the known superstrings are in fact substrings of a single string, and I expect you could find it if you searched.

And that’s as much as I can say without completely giving it away or just going cryptic, I think.

I took your saying “there are no secret random strings” as evidence against that.

...

Guess: Substrings of the hexadecimal representation of the SHA-1 hash of the text of the rule (as DanielH wrote it, not this guess).

Correct!

The emphasis there was on “secret”. The hash was very public; it has appeared on every page of this game.

The rule was Any substring of the SHA-1 hash of this rule.

I don't prefer to set a rule now.

By “now” do you mean “right now” or “the next game”?

If the latter, any of the people who frequent this thread sometimes but haven’t run a game recently?

I meant “I might later but don't hold up the games for it”.

Lambda? Anybody?

If nobody comes forward, should I do a really easy rule to generate a new winner, or just let this thread die?

I could run a game if nobody else wants to and someone wants to play, but I'm on a different time zone from most of you so answers would be slower than you're used to.