Hint for identifier values

README.md

@@ -37,6 +37,12 @@ Import resulting `survey.lss` into LimeSurvey.
 - Put multiple questions into one `randomization_group` to have their order shuffled.
 - Images are included as base64; don't go overboard.
 
+## Hints 
+
+
+- Do not use underscores in the identifier values; that breaks the
+  counting mechanism for correct answers during import 
+
 ## Create Survey (UPB internal) 
 
 - Login to https://umfragen.uni-paderborn.de/index.php/admin