+# Used for giving serial numbers to messages. This can be tied to
+# the msgmap for live updates to living lists (see
+# PublicInbox::Filters::RubyLang), or kept separate for imports
+# of defunct NNTP groups (e.g. scripts/xhdr-num2mid)
+#
+# Introducing NEW uses of serial numbers is discouraged because of
+# it leads to reliance on centralization. However, being able
+# to use existing serial numbers is beneficial.