Spring 1, Year 2, I am talking to several townies, and the dialogue for many of them is if we are dating/married
Zarah, Suki, Wakuu, Leah, Aaliyah, Charles, Yuri, Chaem, and Theo's dialogue was just a standard Happy New Year or a dialogue that seemed appropriate for being friends (Saying they had fun, or asking if I had fun).
Denali, Miranjani, Semeru, Kenny, Pablo, Eva, Alice, Noah, Macy, and Ben all told me they loved me, referenced being partners, or made a reference to doing something at "our" house. (I haven't even unlocked the merfolk relationships yet)
I am only actually dating Raj, Rafael, Mark, and Surya, and their dialogue seemed appropriate for that (Saying they looked forward to spending the year with me or that they had fun, no mentions of love or marriage)
I THINK that's all the dateables.
It happens if I close and reload the game.
Attached are several screenshots.
Steam v 1.1-1198, KBM