Shoo, I just want to make sure I'm understanding your example correctly. So, in what you've asked above, does this mean that B said something before Day 3? Did he try another option before going to the new room (whether that's earplugs, white noise, whatever for himself or something that might help A not snore as loudly)? Was a compromise attempted first or is B going to the new room solution first?
We have several versions of what's being asked here - from the actual OP's situation to some others that we've created since then that I want to get a complete picture of where you are with this. (That's a genuine question to clarify for my own understanding - not a snarky question.)
I'm not sure which scenario I'm arguing, to be honest! In both, I am quite sympathetic to B. He didnt' sleep the first night. Apparently, he thought his sheer exhaustion would help him sleep the 2nd night. When that didn't work, he gave up and got another room. Folks here are blaming him for not getting a new room sooner, or going out and buying ear plugs, or some such thing. I don't really see anybody here blaming A, and I just find that bizarre. A may not be able to do anything about it, but he most certainly is the cause of the problem. Doesn't he bear any responsibility for what he has put B through?
Apparently I am the only one who thinks so. Oh, well.
A is indeed responsible for the problem. But the thing about snoring is that the snorer doesn't know they are snoring. It is entirely possible that A has no idea he/she snores.
So while that doesn't let A off scot-free, it does mean that for A, B's action in taking another, expensive room might have come out of the blue.
So while A has bears the responsibility
for the problem, I don't see A as carrying any blame
Now, if A had been alerted to the problem and then refused to even attempt to do anything about it, A would indeed be blamed for it. But A didn't know, and therefore couldn't try medications or different sleeping positions, or offer to get a separate room, or buy B earplugs or any other possible remedy.
I guess it don't think it is fair to blame someone for a problem they don't know they are causing.
Now, if A knew before the trip that he/she snores like a freight train all night, every night, then I'd put the blame squarely on A. We just don't know that detail.