How about an editable notecard per friend?

I would like to see an option in the Friends menu where I can put (per friend) some text in free format to store any specifics about that friend. Like language to use, home country or other remarks.
Those notes could be stored in the Inventory within a Friends folder or so.

This way i can remove those yellow post-it notes, sticked to my screen now. (Sure, I also could reduce the number of friends I have and remember it all by head...)

You can open that friend's profile, then use the "notes" tab to store text. (In fact you can do this to any resident, not only friends. )