Heh, this topic coming up in a fire emblem forum, when the newest game is basically a cockstroking of the nice guy and the damned romantic supports where everyone likes him for being supposedly nice.
At the same time, reading Brightbow signature with such awesome speeches from the series, makes one think.
Back on the topic.
Back in school, when I was 15, I tried my best to be nice and a good friend of everyone, not just girls, but every person I met in general, talked a lot, always went to greet them, wherever I'd meet, most likely because of loneliness, I lived really far from the city, no neighbors except my cousin.
But then, some time later I noticed most of them, including girls were mostly abusing my behavior, so that made me fucking angry, lol, then I started being outright rude to most, except some that were nice to me as well.
I stayed with that attitude up to later 17 to early 18, where I just said, fuck it, I don't need to be nice, but no need to be rude too. And, well, things got going for me around that time. Found a nice girl, started dating and all.
And, as I grew older, I realized, there are people that are going to suck, no matter what you do and there are also people that are going to be really good to you, if you just be yourself. I could say that there are people that are going to be good no matter what, but I don't believe so, at some moment they're going to learn their lesson.
I don't know if it gets in the topic, as the OP wanted, but I wanted to share my point and story of this.