AutoSpacing

AutoSpacing is an option for StyleBox and Cell which specifies whether spaces between successive characters should be adjusted automatically.

AutoSpacing->False leaves equal spaces between all characters.

AutoSpacing->True inserts additional space around lower-precedence operators.

AutoSpacing->False is in effect automatically used inside ordinary strings and comments.

See The Mathematica Book: Section 2.8.11.

See also: TextJustification.