http://wikisuite.org/tiki-pagehistory.php?page=ClearOS&newver=0&oldver=30
See also attached image
It's a WYSIWYCA bug. Anonymous users can't remove page versions, so interface shouldn't offer it.
@fabio: please coach team as needed
To help developers solve the bug, we kindly request that you demonstrate your bug on a show2.tiki.org instance. To start, simply select a version and click on "Create show2.tiki.org instance". Once the instance is ready (in a minute or two), as indicated in the status window below, you can then access that instance, login (the initial admin username/password is "admin") and configure the Tiki to demonstrate your bug. Priority will be given to bugs that have been demonstrated on show2.tiki.org.