Preferences are good for things that a lot of people want all of the time and a lot of people want none of the time. They're annoying for things that everyone wants only some of the time.
Selecting the nearest space when double-clicking would work for the deletion and dragging cases, but it would fail for the case where you want to retype the word; and it would fail for the case where you want to apply, just to the word, an underline, a background color, or any other formatting that would be visible for the adjacent space. So that selection behavior would be something everyone wants only some of the time, and a preference would not be any help, because changing the preference would be even slower than correcting the mistake.
OpenOffice.org Writer handles this a better way: selecting the word does not select the nearest space, but deleting or dragging automatically deletes or moves the adjacent space as well. That works for the retyping and formatting cases as well as the deleting and dragging cases, and even with OOo's vast array of options, it doesn't have -- or need -- an option for it.