Among all the characters, I sympathise with Sonya the most. She sacrifices herself too much but everyone takes her for granted. I understood her more playing her role on Facebook. Life has been unfair to her. She is an orphan. Nicolas chose Marya over her. And think about this: Marya and she are both the kind and thoughtful type. Nicolas could have chosen her before he meets Marya if she had money.
For sometime, I even feel like she wouldn't have social media if she lived in the modern age. If no one cares, what's the point of posting things on Facebook? And she probably doesn't have strong desire for her voice being heard anyway. That being said, all my Sonya posts weren't necessarily what she had to share with the others. They were more like what she might have in mind.
All my posts were centered around Nicolas and the other Rostovs. Sonya's whole life is about them. She doesn't change much throughout War and Peace; people around her do. She just takes in what has changed and moves on with life. So I figured she would comment on others posts more often than posting her own stuff. Also, Sonya doesn't have strong opinions on things, so her comments wouldn't be against what others have to say.
I gave some thoughts when I chose her profile picture and cover photo. I tried to find a picture of her, but apparently she's not important enough to have pictures all over the Internet. So I chose a cute white cat instead. This actually makes sense since Tolstoy refers to her as cat several times and she might not want herself in the profile picture given her self-abased personality. I was thinking of her affection for Nicholas when I picked her cover photo. It's a red flower in the dark, pure, beautiful but lonely. I was quite surprised when I read the part when Tolstoy calls her a "sterile flower". What a coincidence!