Given beancount:
  2012-12-12 balance Assets:LongLongLongAccount 50.00
  2012-12-12 balance Assets:Cash 50.00
  2012-12-12 balance Assets:Cash -50.00
  2012-12-12 balance Assets:Cash +50.00
  2012-12-12 price EUR 50.00 USD
      metadata: 50
      Assets:Cash  50
      Assets:Cash  50.00
      ! Assets:Cash  50.00
      Assets:Cash         50.00
      Assets:Cash         50.00 USD

Execute (align):
  %AlignCommodity

Expect beancount:
  2012-12-12 balance Assets:LongLongLongAccount  50.00
  2012-12-12 balance Assets:Cash                 50.00
  2012-12-12 balance Assets:Cash                -50.00
  2012-12-12 balance Assets:Cash                +50.00
  2012-12-12 price EUR                           50.00 USD
      metadata: 50
      Assets:Cash                                50
      Assets:Cash                                50.00
      ! Assets:Cash                              50.00
      Assets:Cash                                50.00
      Assets:Cash                                50.00 USD

Execute (change alignment column and align again):
  let g:beancount_separator_col=40
  %AlignCommodity

Expect beancount:
  2012-12-12 balance Assets:LongLongLongAccount 50.00
  2012-12-12 balance Assets:Cash       50.00
  2012-12-12 balance Assets:Cash      -50.00
  2012-12-12 balance Assets:Cash      +50.00
  2012-12-12 price EUR                 50.00 USD
      metadata: 50
      Assets:Cash                      50
      Assets:Cash                      50.00
      ! Assets:Cash                    50.00
      Assets:Cash                      50.00
      Assets:Cash                      50.00 USD