In this case, on the other hand, the ticket is refundable. It is irrelevant that the passenger has checked in and received a boarding pass. Checking in and receiving a boarding pass is not an irrevocable promise to take the flight. On the contrary, the airline's rules completely allow the passenger to cancel the checkin and receive a refund on the ticket. This holds true even after the passenger has used the lounge! (This may be a bad loophole, but it is the rule nonetheless.)
You again mix up the OP's intentions and the rules. Of course there is not a "irrevocable promise" to take the flight you have checked in for. But it is at least the representation that you have a slight intention to take that flight because that is what you say at checkin: "I want to check in for that flight". You would for sure not get a boarding pass if you tell the CIA: "Hei, I do not want to fly but just want to have dinner", would you?
I always use a "thick thumb check" and this is very reliable:
- Would you disclose your plan in details to the contractual counterpart's management (not to a salesgirl)?
- Do you expect the contractual counterpart's management to agree to your plan on full knowledge of the details?
- Are you definitely sure that you are right from an ethical point?
If you cannot answer these questions with a clear "YES" I would be careful. But again the challenge: Who has got the balls to ask LH??? Nobody, because you certainly know their answer and this answer would not please you.