"Your friend [name] has unlocked the achievement: Stellar Set"
"Your friend [name] has gained Shadow Lair 3 clearance"
"Your friend [name] has become the new Level Leader, having completed 150+ levels in the past 7 days"
"Your friend [name] has become the new Crown King, having earned 145k+ crowns in the past 7 days"
and so on…
I do admit some jealousy on my part but if you have to see your superpro friends' insane accomplishments pop up in front of you every single freaking day you'd probably get kind of pissed off after a month of it.
Just don't read it. Pops up at the side, s'not as if it's blaring in your face in big letters. Solution? Close it.
Won't open again until you restart. Easy!