Any time a variable is being set up for output, you can format it using the PHP function number_format($var). I have a hack in the works that does this in a number of places on the site.
For example, suppose (and this is not real vBulletin code) that the total members are stored in $totalmembers. You would add a line to the code somewhere that looks like:
PHP Code:
$totalmembers = number_format($totalmembers);
MAKE SURE that if you do this, the variable you create is
only being used for output. After you call number_format(...), the resulting variable is converted to (or created as) a string.
In other words, code like this would work:
PHP Code:
$somevar = 1050;
$somevar++;
$somevar = number_format($somevar);
// outputs 1,051
echo $somevar . "<br>";
But this code would NOT work:
PHP Code:
$somevar = 1050;
$somevar = number_format($somevar);
// error, $somevar is now a string
$somevar++;
Hope that makes some sense.