An example of splitting a C program into separate characters.

concat-hello.c

#include <stdio.h>
#define X(a,b) a##b
#define x(a,b) X(a,b)
#define s(a) #a

  x   (   i   ,   x   (   n   ,   t
   )   )   x   (   m   ,   x   (   a
    ,   x   (   i   ,   n   )   )   )
    (   )   {   x   (   p   ,   x   (
   r   ,   x   (   i   ,   x   (   n
  ,   x   (   t   ,   f   )   )   )
  )   )   (   s   (   H   )   s   (
   e   )   s   (   l   )   s   (   l
    )   s   (   o   )   s   (   %   )
    s   (   c   )   s   (   W   )   s
   (   o   )   s   (   r   )   s   (
  l   )   s   (   d   )   s   (   !
  )   s   (   %   )   s   (   c   )
   ,   x   (   3   ,   2   )   ,   x
    (   1   ,   0   )   )   ;   ;   }

Unobfuscated code is:

int main() { printf("Hello%cWorld!%c", 32, 10); }

The space has a numeric value of 32 and the newline character is 10, both of them cannot be encoded in the same way as other characters.
The same problem should be expected with parentheses and commas when used in a string.