I thank you for notifying me these details. I added on web site more clarifications about contract. However, the contract is required according to Italian law for renting touristic house in all Italy.
About 100 € deposit, it was reported during your reservation procedure however Airbnb is not allowed to replace the owner in this duty so we have to ask the deposit to our client and give back at check-out if there is no damage.
An additional cost for stay tax of 1 € per night per person has to be considered according to Venice municipality rule. I still add this clarification on web site.
Finally, identity documents are required for registration to police headquarter according to Italian law. I am sorry about misunderstanding I will try to explain better all stuff before approving the reservation next time.
I thank you for your feedback and I wish to host you again in the future.