In Excel 2007:

If one formats a range using the Ribbon: Number group, Number (from the drop
down box), Comma, click the decrease decimal button twice, the cell(s) are
formatted with padding on the right. Using the Format command to view the
applied format, one finds that a custom format has been applied.

If one instead uses the Cells group, Format command (or right click, Format
cells...) and selects Number, comma separator, zero decimals, the cell(s) are
formatted without padding. In this case, no custom format has been applied.

Yeah, I know. Picky, picky. It just pays to be consistent. And attentive.

G