The developer policy states:

It is your responsibility to monitor the use of your service and to design your service to prevent violations of Twitter policy by people who use it. Failure to do so may result in suspension or termination of your API and Twitter Content access.

Unsolicited mentions are a violation of policy, so you should design your system to avoid users responding to Tweets they are not mentioned in, and educate your users that this is against Twitter’s policies.

You can read more about this policy here.