We have Jobs with timer trigger and SCM timer trigger.
Every trigger has an comment like this:

# every 30 minutes
*/30 * * * *

If we copy jobs with these triggers by URL(<Jenkins-URL>/createItem?name=copyOfJob) and config.xml as post data, then the triggers are not activ. Jenkins handles

# every 30 minutes
*/30 * * * *

as a whole comment.

If the trigger configuration ist like:

*/30 * * * *
# every 30 minutes

then copy by URL ist not possible. Jenkins gives an Exception (see Attachment)