There is a rumour circulating on Facebook that if you type BFF in comments, and it shows up in green, then it means your Facebook account is secure.
THIS IS A HOAX!
Although it is true that Facebook comments including the word “BFF” in green are among known animations, its appearance (or lack thereof) is not related to account security in any way. A missing green “BFF” does not indicate anyone’s account was compromised ay any point, and instead most likely relates to browser settings
This article explains: