Unfortunately, there is no way according to this thread: http://community.tableau.com/thread/124856?start=0&tstart=0
Other features, like the Comments section, are only editable as a Permission and NOT a global setting, which means it has to be disallowed at the Project, Group, User, etc level.
This is a huge pain if you ask me. Consider voting up ideas related to this issue:
Thanks. I actually removed the permissions for comments so the comments section disappeared but the tags are still there
I know. And its a pain, as space is limited as it is. Do what you can to encourage Tableau to provide more options for Server settings!
Thank you. I will vote for it for sure