The letters S and N have point symmetry but not line symmetry.
b
O h
I could be wrong but I believe the following have point symmetry: I H O X That means if you cut them in half vertically or horizontally the pieces would be the same, mirror images if you will. There are many more letters that are symmetrical down a vertical line such as M and W etc.
The list provided with the question doesn't include any letters that meet the requirements.
Letters that have a vertical line symmetry: WTYUIOAHXVM Letters that have a horizontal Line symmetry: EIODHKCB
Possibly the letters with no lines of symmetry.
A, B, C, D, E, H, I, K, M, O, T, U, V, W, X, and Y all have point symmetry
Line symmetry = Reflection symmetry. Point symmetry = Rotational symmetry.
all letters have a line of symmetry
This is different in different typefaces (fonts) but in arial: o i l s v w x z all have symmetry s and z have point symmetry the others have at least one line of symmetry.
It is a line through the point of symmetry. In general it is not an axis of symmetry.