If you precede a number by a comma, the comma *will* be displayed (or at
least it will in my version of Excel).
If you want a number in a cell to be formatted as text, precede it with an
*apostrophe*, which will *not* be shown.
If you have a cell containing a number, and you want it converting to text
(perhaps to maintain format while exporting to Word mail merge, for
example), then use the TEXT() function.