Most of what you guys said is what I was going to write about; flaws, not going too far with drama/powers/anything else. However, one of the things that usually make the RP VERY unrealistic, even silly sometimes is when one of the charries read the other's mind. I know sometimes you make that mistake once or twice, I know I did a couple of times myself, but doing it constantly proving that your character is a sharp eye reader or something like this is way too unrealistic to me.
That is why, actually, I prefer to bold the dialogue out in my post so that the other person will catch what their character should be replying to instead of getting distracted or something. It also helps anyone who wants to have a double-personality character; someone who knows how to sweet-talk everyone when they have a bitter spirit within.
This and relationships, especially ones starting at ages 11,12,13
I'd say up to 16 Those, in my opinion, should be relationships based on instinct and hormones rather than deep understanding of life and love.
This is not something I really care about that much so long it doesn't affect any of my characters but I wanted to draw the attention to it again. My Hogwarts girl got her first kiss when she was fifteen and she doesn't even have a stable relationship, always struggling for love and promises and craving them too! But I don't think it'll be realistic for her to figure things out before at least her graduation.
I don't see how religious expressions got into the discussion of realistic RPing so I'm not going to comment on that, I just agree with
Tommehbell on what she said in her last post.