I set lead type as a hobby, and I can tell you the entire concept of a "space character" does not exist in typesetting. Space is not made of characters, it's made of space (in metal, it's made of tiny shims of copper, brass, or lead).
Any use of the space bar in a computer typesetting context is just a hint to some algorithm regarding how much space you want put between the characters on either side. TeX doesn't put "1.5 spaces" between sentences; it puts glue that is slightly stretchier than the glue it puts between words.
Any use of the space bar in a computer typesetting context is just a hint to some algorithm regarding how much space you want put between the characters on either side. TeX doesn't put "1.5 spaces" between sentences; it puts glue that is slightly stretchier than the glue it puts between words.