"I'm Fine": When One Partner Speaks in Weather and the Other in Sentences

You asked what was wrong. They said nothing. You went back to your phone, and now you are the bad guy, because you believed them. They said "I'm fine" and you took the words at face value, the way you take all words, and apparently that was the wrong thing to do. They wanted you to push, to ask again, to read the posture, the silence, the way they set the glass down a little too hard. You saw none of it, not because you don't care, but because you process words, not signals. They handed you a code and you read it as English.
They built a wall and resented you for not climbing it. You respected the wall because you thought that was love. And now you're both lying in the same bed, them thinking you don't care, you thinking everything is fine. They speak in weather. You speak in sentences. Neither language translates, and the gap between what they meant and what you heard is where the relationship is slowly dying. It is not fine. But nobody told you that in words you could understand.
The trait is Emotionality and attunement
This is a difference on the Emotionality facet, which shapes how much a person communicates and reads emotion through indirect signal versus explicit statement. The high-Emotionality partner naturally encodes feeling in tone and body language and expects it to be read; the lower-Emotionality partner naturally trusts literal words and doesn't scan for subtext. Neither is a communication failure. They are two different channels, and "I'm fine" is the exact frequency where they fail to meet.
The fix requires both to translate: the signal-sender has to risk saying the plain sentence, and the word-reader has to learn that "I'm fine" from this particular person means "ask again." You will not turn one into the other, but you can agree that the important things get said in words, so the relationship stops running on a code only one of you can read.
Where each of you sits on the Emotionality facet that decides whether you speak in signals or sentences is measured by the 30-facet OCEAN personality test in about 15 minutes, with domain results free, and a compatibility report shows why "I'm fine" keeps starting fights nobody meant to have.