Writing threads with myself for plot??

Hullo there... 

I saw a question in here about writing with one's self for trades (not allowed, understandably). I wanted to know if we could write with ourselves just for plot purposes? Self-fulfilling plot purposes? It would only be to develop character, you see. 

Apologies if this has already got an answer somewhere. I tried doing a little search (didn't try awfully hard though aha).