I think you need to have a star to be a Sage. Sages have 170+ (like me--hooray), but also have that track record of posting serviceable information here.
I'm not actually sure what the requirements are to be a sage, but you do indeed receive a star when site staff have observed you to be a very helpful, active, and insightful member on the forums over a period of time.
'Is it possible to unchecked a lesson ? I wanna remove the green heck mark because I accidentally went through the lesson but didn't finish it . Would rather not star it since that means " important / focus on again/ confusing " in my head.