more comments

Firmware/Marlin_main.cpp

@@ -181,6 +181,8 @@ float homing_feedrate[] = HOMING_FEEDRATE;
 
 //Although this flag and many others like this could be represented with a struct/bitfield for each axis (more readable and efficient code), the implementation
 //would not be standard across all platforms. That being said, the code will continue to use bitmasks for independent axis.
+//Moreover, according to C/C++ standard, the ordering of bits is platform/compiler dependent and the compiler is allowed to align the bits arbitrarily,
+//thus bit operations like shifting and masking may stop working and will be very hard to fix.
 uint8_t axis_relative_modes = 0;
 
 int feedmultiply=100; //100->1 200->2