YES

Problem:
 rev(a()) -> a()
 rev(b()) -> b()
 rev(++(x,y)) -> ++(rev(y),rev(x))
 rev(++(x,x)) -> rev(x)

Proof:
 Matrix Interpretation Processor: dim=1
  
  interpretation:
   [++](x0, x1) = 4x0 + 4x1 + 1,
   
   [b] = 0,
   
   [rev](x0) = x0,
   
   [a] = 0
  orientation:
   rev(a()) = 0 >= 0 = a()
   
   rev(b()) = 0 >= 0 = b()
   
   rev(++(x,y)) = 4x + 4y + 1 >= 4x + 4y + 1 = ++(rev(y),rev(x))
   
   rev(++(x,x)) = 8x + 1 >= x = rev(x)
  problem:
   rev(a()) -> a()
   rev(b()) -> b()
   rev(++(x,y)) -> ++(rev(y),rev(x))
  Matrix Interpretation Processor: dim=3
   
   interpretation:
                   [1 0 0]     [1 0 0]     [0]
    [++](x0, x1) = [0 0 0]x0 + [0 0 0]x1 + [1]
                   [0 1 1]     [0 1 1]     [0],
    
          [0]
    [b] = [1]
          [0],
    
                [1 1 1]  
    [rev](x0) = [0 1 0]x0
                [1 0 1]  ,
    
          [0]
    [a] = [0]
          [1]
   orientation:
               [1]    [0]      
    rev(a()) = [0] >= [0] = a()
               [1]    [1]      
    
               [1]    [0]      
    rev(b()) = [1] >= [1] = b()
               [0]    [0]      
    
                   [1 1 1]    [1 1 1]    [1]    [1 1 1]    [1 1 1]    [0]                    
    rev(++(x,y)) = [0 0 0]x + [0 0 0]y + [1] >= [0 0 0]x + [0 0 0]y + [1] = ++(rev(y),rev(x))
                   [1 1 1]    [1 1 1]    [0]    [1 1 1]    [1 1 1]    [0]                    
   problem:
    
   Qed