My balance sheet is unbalanced, what I dot not find appropriate from an
accounting point of view...
It seems that realized gains or losses on commodities are not included in
the balance sheet.

A very simple example: 

1. you earn $1000 on Jan 1st :
   $1000 on Bank from Revenue
2. you buy 100 stocks a $8 with the money in the bank on Jan 2nd
   $800 on Stock from Bank
3. you sell your stocks at $10 on Jan 3rd, you're lucky
   $1000 on Bank from Stock

the resulting default "balance sheet" after Jan 3rd looks like :

1. Assets
   bank $1200
   stock $0
   total           $1200
2. Liabilities     $0
3. Equity
   initial $0
   profit $1000
   total           $1000

I wish I had a "commodity profit" line of $200 somewhere so as
to get a balanced balance... As the "unrealized gains/losses" can
be computed, I guess the realized ones could also be computed!