Clarify comments about parameter versioning

ROMFS/px4fmu_common/init.d/rcS

@@ -36,9 +36,10 @@ set SDCARD_FORMAT no
 set STARTUP_TUNE 1
 set VEHICLE_TYPE none
 
-# Airframe parameter versioning: airframe maintainers can optionally set this in the
-# airframe startup script, and then increase it by one whenever they want to ensure
-# that parameters are reset to the airframe defaults for an update.
+# Airframe parameter versioning
+# Value set to 1 by default but can optionally be overridden in the airframe configuration startup script.
+# Airframe maintainers can ensure a reset to the airframe defaults during an update by increasing by one.
+# e.g. add line "set PARAM_DEFAULTS_VER 2" in your airframe file to build the first update that enfoces a reset.
 set PARAM_DEFAULTS_VER 1
 
 #
@@ -236,8 +237,8 @@ else
 	fi
 	unset AUTOSTART_PATH
 
-	# Check parameter version and reset upon airframe configuration version mismatch
-	# reboot required because "param reset_all" would reset all "param set" lines from airframe
+	# Check parameter version and reset upon airframe configuration version mismatch.
+	# Reboot required because "param reset_all" would reset all "param set" lines from airframe.
 	if ! param compare SYS_PARAM_VER ${PARAM_DEFAULTS_VER}
 	then
 		echo "Switched to different parameter version. Resetting parameters."

src/lib/systemlib/system_params.c

@@ -88,8 +88,8 @@ PARAM_DEFINE_INT32(SYS_HITL, 0);
  *
  * This is used internally only: an airframe configuration might set an expected
  * parameter version value via PARAM_DEFAULTS_VER. This is checked on bootup
- * against SYS_PARAM_VER, and if they do not match, parameters from the airframe
- * configuration are reloaded.
+ * against SYS_PARAM_VER, and if they do not match, parameters are reset and
+ * reloaded from the airframe configuration.
  *
  * @min 0
  * @group System