Sometimes I don't comment, thinking that some people might take the comment the wrong way, but then today I just saw an entire comment section in yt get offended because the person in the video called vanilla ice cream "plain".
So... I learned that no matter what you say, no matter how non-issue it is, it will be escalated worse than you ever intended.
(Not to say you should just comment everything from your head, but just know that even if you already took measures to try not to hurt someone with your take on something, someone out there is still going to see that as a personal offense).
They didn't confirm if best friend and the sister kissed or if FL was just seeing things at an angle. But, most likely he did actually kiss the sister and they just cut the flashback from there since we already saw it at Ch. 3