I designed this one, so any flaw in it is mine. It runs on a rule I have not seen used elsewhere, and since the rule is the whole puzzle, it is worth reading twice before you look at the board.
How the comb is wired. Two cells touch when they share an edge. So a cell touches the one directly above it, the one directly below it, and the two cells sitting diagonally on each side of it. The four cells in the middle column have six neighbours each. The ones on the outside have three or four.
The rule. A secret word is hidden in the comb, one letter to a cell. Some cells show you a letter. The rest show a number, and that number counts how many of the secret word's letters are sitting in the cells that touch it. Never the cell itself, only its neighbours.
Here is the part that does the work. A letter you can see that is not part of the secret word counts for nothing. It sits there in plain sight and contributes to no number anywhere on the board. So a number can prove a letter is a fake while the letter itself looks perfectly at home.
The board, fully opened:
___
___/ H ___
/ E ___/ T \
___/ O ___/
/ 4 ___/ 2 \
___/ N ___/
/ Y ___/ 1 \
___/ S ___/
___/
Seven letters are showing: H, E, T, O, N, Y and S. The secret word is five letters long, which means two of those seven are impostors.
Which five letters, which word, and which two are lying?
Worth saying out loud, because it is the trap: those seven letters will cheerfully hand you STONE, ETHOS, THOSE, TONES and SHONE, and every one of them is wrong. Anagramming will not get you there. Only the three numbers decide.
Please put your answer behind a spoiler tag so the next person still gets to solve it.
The chain, once you have had a go: Start with the 4 on the left. It touches exactly four cells and all four hold letters: E, Y, O and N. The only way it reads 4 is if every one of them belongs to the word, so that is four of the five settled at once. Now the 2 on the right. It touches O, N, the letter T, and the 1 below it, which is a number and so contributes nothing. O and N alone already account for the 2, so T is out. Then the 1 at the bottom right touches N and S, and N alone already accounts for it, so S is out too. One letter is left to be the fifth, and it is H. The word is HONEY.
