-this flag is TRUE at the end of an address, then if an extraneous semicolon is
-found, it is ignored and the flag is cleared. This logic is used only when
-scanning through addresses in headers, either to fulfil the -t option or for
-rewriting or checking header syntax.
+this flag is TRUE at the end of an address, and if an extraneous semicolon is
+found, it is ignored and the flag is cleared.
+
+This logic is used only when scanning through addresses in headers, either to
+fulfil the -t option, or for rewriting, or for checking header syntax. Because
+the group "state" has to be remembered between multiple calls of this function,
+the variables parse_{allow,found}_group are global. It is important to ensure
+that they are reset to FALSE at the end of scanning a header's list of
+addresses.