So, ... imagine you're scrolling through Instagram and find a cool picture that a friend of yours might like. What do you do? Probably you'll comment the picture with "@name_of_your_friend_here".
And what happens if your comment looks something like "Cool, looks like your work! ... @name_of_your_friend_here". On a normal situation that would be a compliment for both artists, but if the guy that posted the pic has a tight ass he will block both you and your friend, from being followers.
When questioned about it:
"Your friend accused us of plagiarism, as a precaution to volatile situations on social media we usually block to eliminate this issue."