As an INFP, I will say this does not register with me either - I'm extremely guarded with feelings, and the other person has to iniate such expressions first, and even then I return them somewhat awkwardly. I'm even 10x more guarded with such expressions IRL than online.
I'd suggest INFJ, as they can look like INTPs to people and sometimes test INTP. Of all the INXXs, they come across the most warm/affectionate when you actually get them to talk, IMO.
That said, I knew an INTP who was much more expressive of affection than I am ( actually, I know a few like this). However, over time, it seemed to me that the feeling behind the expression was rather shallow & even short-lived- maybe even expressed out of a sense of obligation or appropriateness. Inferior Fe maybe? These expressions came quite surprisingly easily from him, but they were also retracted quite easily. He even admitted to this trait of expressing strong feelings in a moment, but then they would fade quickly and he'd be over it & back to his cold self. It's misleading to the receiver....