Code style and comment tweaks

Marlin/src/HAL/HAL_DUE/HAL_SPI.cpp

   }
 
   // all the others
-  static uint32_t spiDelayCyclesX4 = (F_CPU) / 1000000; // 4uS => 125khz
+  static uint32_t spiDelayCyclesX4 = (F_CPU) / 1000000; // 4µs => 125khz
 
   static uint8_t spiTransferX(uint8_t b) { // using Mode 0
     int bits = 8;

Marlin/src/HAL/HAL_DUE/usb/uotghs_device_due.c

 	// The IN data don't must be written in endpoint 0 DPRAM during
 	// a next setup reception in same endpoint 0 DPRAM.
 	// Thereby, an OUT ZLP reception must check before IN data write
-	// and if no OUT ZLP is recevied the data must be written quickly (800us)
+	// and if no OUT ZLP is received the data must be written quickly (800µs)
 	// before an eventually ZLP OUT and SETUP reception
 	flags = cpu_irq_save();
 	if (Is_udd_out_received(0)) {

Marlin/src/HAL/HAL_ESP32/i2s.cpp

    *
    *   fwclk = fbclk / 32
    *
-   *   for fwclk = 250kHz (4uS pulse time)
+   *   for fwclk = 250kHz (4µS pulse time)
    *      N = 10
    *      M = 20
    */

Marlin/src/HAL/HAL_ESP32/timers.h

 
 #if ENABLED(I2S_STEPPER_STREAM)
   #define STEPPER_TIMER_PRESCALE     1
-  #define STEPPER_TIMER_RATE         250000                           // 250khz, 4us pulses of i2s word clock
+  #define STEPPER_TIMER_RATE         250000                           // 250khz, 4µs pulses of i2s word clock
   #define STEPPER_TIMER_TICKS_PER_US ((STEPPER_TIMER_RATE) / 1000000) // stepper timer ticks per µs // wrong would be 0.25
 #else
   #define STEPPER_TIMER_PRESCALE     40

Marlin/src/HAL/HAL_LPC1768/u8g/LCD_delay.h

  *
  * These are based on the LPC1768 routines.
  *
- * Couldn't just call exact copies because the overhead resulted in the
- * one microsecond delay being about 4uS.
+ * Couldn't just call exact copies because the overhead
+ * results in a one microsecond delay taking about 4µS.
  */
 
 #ifdef __cplusplus

Marlin/src/MarlinCore.cpp

   #if PIN_EXISTS(FET_SAFETY)
     static millis_t FET_next;
     if (ELAPSED(ms, FET_next)) {
-      FET_next = ms + FET_SAFETY_DELAY;  // 2uS pulse every FET_SAFETY_DELAY mS
+      FET_next = ms + FET_SAFETY_DELAY;  // 2µs pulse every FET_SAFETY_DELAY mS
       OUT_WRITE(FET_SAFETY_PIN, !FET_SAFETY_INVERTED);
       DELAY_US(2);
       WRITE(FET_SAFETY_PIN, FET_SAFETY_INVERTED);

Marlin/src/module/configuration_store.cpp

   #endif
 
   #if HAS_BED_PROBE
-    constexpr float dpo[XYZ] = NOZZLE_TO_PROBE_OFFSET;
+    constexpr float dpo[] = NOZZLE_TO_PROBE_OFFSET;
     static_assert(COUNT(dpo) == 3, "NOZZLE_TO_PROBE_OFFSET must contain offsets for X, Y, and Z.");
     #if HAS_PROBE_XY_OFFSET
       LOOP_XYZ(a) probe_offset[a] = dpo[a];

Marlin/src/module/stepper.cpp

           // Don't step E here - But remember the number of steps to perform
           motor_direction(E_AXIS) ? --LA_steps : ++LA_steps;
         #else
-          step_needed[E_AXIS] = delta_error.e >= 0;
+          step_needed.e = delta_error.e >= 0;
         #endif
       }
     #elif HAS_E0_STEP
 
     #if DISABLED(LIN_ADVANCE)
       #if ENABLED(MIXING_EXTRUDER)
-        if (step_needed[E_AXIS]) E_STEP_WRITE(mixer.get_next_stepper(), !INVERT_E_STEP_PIN);
+        if (step_needed.e) E_STEP_WRITE(mixer.get_next_stepper(), !INVERT_E_STEP_PIN);
       #elif HAS_E0_STEP
         PULSE_START(E);
       #endif