Modern markup
Mostly a subset of WikiCreole, except with a completely different LinkSyntax.

Modern HTML
Generated pages normally validate as HTML5 (though it's possible to break that), and CSS is supported. We're not in 1995 anymore.

UTF-8 support
While page names are restricted to ASCII characters, page contents are handled as UTF-8, permitting a wide range of characters.

Page transclusion
Can be used as a poor man's redirect, plus other things.

Flat-file storage
Pages are saved as ordinary text files on disk, making them easy to backup, inspect or change from outside WabiSabi.

Page backups
The previous two versions of any page are saved. A future release will probably offer access to them.

Captcha
The simplest possible system, based on a fixed password. Before you ask, yes, this is effective, and also allows for a non-public wiki simply by hiding the password.

Recent changes
On the other hand, it should be easy to watch when pages are changed, in order to catch vandalism quickly.

Universal Edit Button
See http://universaleditbutton.org/Universal_Edit_Button

Plugin support
Allows creating extra wiki actions and markup plugins, and replacing or modifying the built-in templates, without any changes to the core file.

Plugins

Wanted pages
Finds and displays all links to non-existent pages on the wiki.

RSS newsfeed
Renders the recent changes as a newsfeed in RSS format, making it easy to monitor automatically. .