In my experience, way people act in a relationship long term is frequently is more comparable to how people act around strangers than within an existing social group. Common example of this would be if you’re on a date with a stranger and they just randomly leave, are mean to waiting staff, etc — though they would not likely exhibit that same negative behavior the date was from a existing social group because of the negative blow back.

Also, I agree, the whole love at first sight is for sure a very real pattern, and uncommon for friendships to develop into something more. That said, in truly long term relationships, vast majority of those types of feelings significantly fade after the “honeymoon” phase of a relationship. Further, if someone is with you for example financial reasons, it’s much less likely they’ll stick around if financial hardships are experienced or they find someone else with significantly more financial resources.

My thesis is not so much to grow friendships into non-platonic relationships, but that relationship attributes are predictable among platonic and non-platonic relationships and that by requiring someone build a “relationship reputation” first, then when engaging other users in the context of going on a date, there’s a much higher chance that they’ll actually have relationships skills.

Whole shared interests aspect is also a frequently sighted as a desirable aspect of a relationship, though rarely good predictor of relationships skills.