Are we allowed to make the same dishes twice in this game? Or is there some disadvantage to it, like having it not count toward your total?

The game will tell you that you have already made a dish if you try to make it a second time, and you cannot make it again.

The good news is that you don't waste your ingredients if you inadvertently duplicate a dish, which is quite easy to do once you've made a few.

"Did you know that at least one player has successfully made every single dish?"
Is a message that I got at least three times.
Congratulations to the player that has managed to make all the recipes but can we please have a meaningful hint?

The wording is funny there but it has been changed recently. It was originally set up to read something like "Did you know no one has yet made (X)?"

And (X) would be filled by a randomly picked, never made recipe. However once all of them had been made it read "Did you know no one has ever made ". And people were freaking out about lack of closure on that broken sentence.

So I could be wrong but I think it is not bragging about a single player, but rather it is just an override of the above message saying the same thing; that all current recipes have been made at least once. Either way it is a meaningful hint for innovator badgelet purposes

Yes, I am sure it was likely just a text edit rather than changing the code to take out that instance appearing. If Terry wants to go in and mess with it further, I wouldn't oppose. It's definitely on the minor scale.

I'm sure everyone will give me a "Well, duh" kind of look for saying this, but in the off chance there are any aspiring chefs who haven't noticed, some recipes have more hints than just what the Crazed Chef says. If you look at "Who's Made What?", some descriptions are generic or amusing, while others give clear clues about one or more ingredients that go into a dish. It's a good resource to try if you're feeling stuck.