Sounds to me like your boyfriend was just teasing him as he knows better. I wouldn't worry about it. I'm sure it's harmless.
What was this all about? I updated a photo on Facebook and I had my boyfriend and a few other guys comment. One guy commented saying "Ilu" I ignored it. Later my boyfriend replies to him saying "best comment". I'm confused.
ILU=I love you?
Why did you only have your boyfriend and a few other guys comment on it? Why don't you ask your boyfriend why he commented like he did?
