The use of comments and posts is a key element of engagement in the use of social media.
When setting up a new initiative, investigate what options, if any, are available to you for monitoring comments and then ensure that you monitor comments and posts regularly (at least once a day) and respond accordingly.
Do not delete negative or critical comments as this diminishes the credibility of the community you have created. Rather, consider responding appropriately and refer to existing processes that are in place should it be a complaint.
You should, however, delete any comments or posts that are defamatory, based on unsubstantiated claims, infringe on another member's privacy, are based on unsolicited advertising or are of an abusive nature. Sometimes comments deleted may need to be dealt with outside of the social media environment. Check with your supervisor in the first instance.
It is a good idea to publish a disclaimer that outlines what posts you will remove.