noted

src/hardware/keyboard.cpp

@@ -2252,6 +2252,16 @@ uint8_t p7fd9_8255_mouse_latch = 0;
 uint8_t p7fd8_8255_mouse_int_enable = 0;
 
 void pc98_mouse_movement_apply(int x,int y) {
+    /* NTS: Contrary to initial impressions, bus mice do not clip
+     *      the counter values to stay within signed integer range,
+     *      they just count.
+     *
+     *      Also newer hardware is said to auto-reset the counter
+     *      when reading, instead of on bit 7.
+     *
+     *      According to Nanshiki: [https://github.com/joncampbell123/dosbox-x/pull/4697]
+     *
+     *      -- 2023/12/21 J.C. */
     p7fd9_8255_mouse_x += x;
     p7fd9_8255_mouse_y += y;
 }