Do best friends have to "add you back"?

Solution 1:

Apparently yes? A friend added me as a best friend and I show up in his list, but I forgot to add him, and he does not show up in my list. So be sure to make sure both parties add each other as best friends! You CAN add best friends without reciprocating, but in that case you will know when they're online but they won't know when you're online.

I am unsure if you can send messages to friends who haven't reciprocated a best friend request at this moment.

Note your friend will need to enable sharing their online status; click the "friends list" icon and click the big "on" button. You may need to change your Parental Controls settings to enable this, even if parental controls are off you aren't allowed to share online status in ACNL before explicitly enabling a parental control option.