Should progn change the behaviour of forward-char with diacritic characters?

[Dan Maftei]

Create a character using a combining diacritic (Unicode plane 0x300-0x36f):

e C-x 8 <RET> 0306 <RET>

Place point before the character. Execute (point), then move forward one-character, and execute (point) again. Notice its value changes by two.

Now do the same, but execute (forward-char) inside a progn or defun statement. Why does point only move forward by one? For example, place point before the character, and execute:

(progn (message "%d" (point)) (forward-char) (message "%d" (point)))

Thanks,

Dan