The hint goes something like this:
"Once in a blue moon, the hint system ... and usually requires combining three clues to get the next logical step in the solution."
I only remember the "Once in a blue moon" part. When I got that hint, I got the impression that I had arrived at the most cherished part of the puzzle treasure vault.
I had stumbled across a real stumper, gotten stuck at the right place, hit the hint button at the right time, and I didn't get charged a penalty.
And after all that, I got to spend some more quality time with the puzzle.
I have only seen that hint message once while attempting one of the challenging category 4x7 puzzles. If I get it again, I'll take better notes.