[nullve]

The Woodson 1N opening (which shows a balanced hand with either 10-12 or 16-18 hcp) is not great when Responder has something like 8-11 bal. without a 5-card major. But suppose that with this hand type Responder, instead of always bidding (just in case Opener has 16-18, but at the risk of having to play 2N on a combined 18-23 count), tries to guess whether partner has 10-12 or 16-18 based on RHO's reaction to the 1N + alert. Would that be a form of coffeehousing, or just on a par with playing the jack from KJTx in hand opposite A98x, waiting for LHO's reaction before deciding which way to finesse?

[barmar]

Coffeehousing is when you change your tempo to try to unsettle another player or mislead them about your hand, perhaps to induce a tell from them. Just trying to read their reaction to a bid is not illegal. You're allowed to take inference from an opponent's tempo or mannerism, but at your own risk.

I'm not sure how much inference you can take from an opponent's reaction to an unusual convention like this.

[Zelandakh]

nullve, on 2017-December-25, 10:20, said:

But suppose that with this hand type Responder tries to guess whether partner has 10-12 or 16-18 based on RHO's reaction to the 1N + alert

Are you going to call the director when you guess wrongly claiming that RHO tried to mislead you?

[chrism]

You would have to avoid violating 74C5, which forbids "looking intently at any other player during the auction and play, or at another player’s hand as for the purpose of seeing his cards or of observing the place from which he draws a card" ...

I would not want to play a method that relies on Old Black Magic table feel if I could see my partner. It raises too many questions when you consistently guess right, however ethically you actually play it.

The method is also not usable if sitting North/South behind screens.