fixup! fixup! X509_dup.pod: add caveat that extra data is not copied …

…and hints, e.g., to use X509_up_ref() instead

doc/man3/X509_dup.pod

@@ -360,13 +360,12 @@ binary data using B<d2i_I<TYPE>>().
 
 B<I<TYPE>_dup>() copies an existing object, leaving it untouched.
 Note, however, that the internal representation of the object
-may contain extra data besides the ASN.1 structure.
-For instance, an B<X509> object usually is augmented
-by cached information on X.509v3 extensions, etc.
-Such extra data is not copied.
-If it needs to be retained, it may be better to use B<I<TYPE>_up_ref>().
+may contain besides the ASN.1 structure further data, which is not copied.
+For instance, an B<X509> object usually is augmented by cached information
+on X.509v3 extensions, etc., and losing it can lead to wrong validation results.
+To avoid such situations, better use B<I<TYPE>_up_ref>() if available.
 For the case of B<X509> objects, an alternative to using L<X509_up_ref(3)>
-is to still call B<I<TYPE>_dup>(), e.g., I<copied_cert = X509_dup(cert)>,
+may be to still call B<I<TYPE>_dup>(), e.g., I<copied_cert = X509_dup(cert)>,
 followed by I<X509_check_purpose(copied_cert, -1, 0)>,
 which re-builds the cached data.