the quick and dirty way is to use spaces between bold characters. this is a simple great quick and dirty trick.
for some reason the bold character from mIRC is fucking up this window, but use two bold characters(control-b) with a space between them to make a space. use as many as you want it works with echo try it, just make sure you have an EVEN about of bold characters
edit: I don't even know what you'd need multiple spaces for other than formating.
edit try this:
//echo -a this is normal text
//echo -a $chr(2) $+ $chr(2) this is a single space
//echo -a $chr(2) $chr(2) this is two spaces
//echo -a $chr(2) $chr(2) $chr(2) $+ $chr(2) This is three spaces.
etc, just make sure the bold chars, $chr(2) are paired in twos, otherwise the text will be bold.