Cleanup: consistent use of tags: NOTE/TODO/FIXME/XXX

Also use doxy style function reference `#` prefix chars when
referencing identifiers.

source/blender/editors/space_image/image_buttons.c

@@ -511,7 +511,7 @@ static bool ui_imageuser_pass_menu_step(bContext *C, int direction, void *rnd_pt
     return false;
   }
 
-  /* note, this looks reversed, but matches menu direction */
+  /* NOTE: this looks reversed, but matches menu direction. */
   if (direction == -1) {
     RenderPass *rp;
     int rp_index = iuser->pass + 1;