stosb = store sequential byte increments the destination pointer, just like lodsb increments the source pointer.
Also, eww. It decrements or increments dependent upon a flag. Not nice.
99% of the time the flag is clear... unless it isn't.
So for a seasoned assembly programmer that cld is idiomatic, axod probably typed the instruction reflexively because he knows he can't rely on the state of the direction flag, even if it has nothing to do with the problem per-se.