A Microsoft spokesperson emailed the following statement to CNET:
The recently released Twitter for Zune HD application has been abbreviating some explicit words in tweets when viewed on the device. However, these explicit words do appear in their full text on the Twitter site or on any other Twitter client. We have identified the issue and are taking steps to update the application as soon as possible to ensure that Twitter for Zune HD users are able to view tweets in their original state.
Viva la resistance!