This is fascinating. I was trying to figure out why I’ve never run into this issue (at least not consistently enough to notice it despite copious amounts of online dating) and realized it is because I don’t try to find common ground. I find common ground in dates often rather boring; if I interject to agree, I’m happy to have them continue to talk after acknowledging my agreement because…well, what else is there to say? I’m likely to do the same if the roles were reversed with the (perhaps not shared) caveat that if I’ve been talking for a while I’ll notice and ask them a question.
But the vast majority of my interjections aren’t agreement. They’re either active disagreement or clarifying questions with a hint of disagreement. And debate ensues that is often more meta than specific so it doesn’t really feel like “his” topic anymore.
Anyway, just wanted to add my perspective since I was initially struggling to relate.