I see your question on the [ indent ] tag has been answered.
As for the leading spaces, your Web browser eats them. The HTML specifications say that any block of spaces gets turned into a single space. Spaces at the beginning of a line are removed completely.
As for inserting extra spaces: There are two ways to go about that: If it’s a separate part of something, you’re best bet is to wrap that separate part in
tags, which will preserve all spaces (although you'll lose wordwrap). However, if it's an intrinsic part of your post, your only recourse is to use junk text, and use the [color] tag to make it invisible.
Examples:
Apple ...........................Pear
Red .............................Green
Note that I used [color=#f8f8f8] not [color=white]. On some monitors you can tell the difference.
The only problem with that is, as vBulletin handles it, the input area now contains regular spaces, not the HTML coding. If you want to make changes and retain the coding, you can navigate to the previous page. However, if you used the quick reply box, the text you entered there is not restored (at least that’s what happened when I tried it just now).