I am not sure what you mean by web characters impacting worklist items? Can you explain the scenario that are asking about?
As for functionality within K2 to transform characters, no there is no such special feature, however if you are looking to change data that is contained within a K2 data field, you can leverage a Server Event within the process and write .NET code to do what you need.
For example, within the Server Event the following could be used to change the ocurrences of "&" to "&" within the contents of a Process Data Field called 'MyField':
K2.ProcessInstance.DataFieldsl"MyField"].Value = K2.ProcessInstance.DataFieldsl"MyField"].Value.ToString().Replace("&","&");