Add comment to avoid ACKS losing order (GH-17678)

diff --git a/Misc/ACKS b/Misc/ACKS
index de532fc..8ab7a6c 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1901,3 +1901,5 @@
 Gennadiy Zlobin
 Doug Zongker
 Peter Åstrand
+
+(Entries should be added in rough alphabetical order by last names)