If you have a poem that does not tell a story or have a particular meaning then then maybe post it in the 'nonsense poetry' category. If you believe your poem tells a particular story and is more than say 8 lines in length and is being flagged, email the HP team, let them have a look at it.
Flagging is usually done by the readers so the staff will take a look at it. The reason for the flagging will be displayed on top of the hub. Read the reasons carefully and make the changes. If you do not understand then send an Email in and I assure you will get an answer.
Try not to make the poem too short.