Wiki Creole
You can read in detail here, http://www.wikicreole.org/wiki/Creole1.0, but basically, Wiki Creole attempts to provide a standard, "familiar" markup across different wiki engines (turns out to have been either mostly ignored, or effectively replaced by Markdown, but whatever).
So instead of learning PmWiki.BasicEditing markup, maybe you already know Wiki Creole or it looks better to you. In that case, you can write pages on this wiki using Creole Markup, as it is supported.
To take a quick look, here is their "cheat sheet":

Wiki Creole 1.0 Cheat Sheet
Wikie Creole is different, I guess if each page uses different mark up it may be a little more overhead to edit them, so should probably pick a standard for editors.
Main obvious differences from PM Wiki? markup look like:
- use of double asterisks **...** for bold instead of triple-quote '''...'''
- use of double slash //...// for italic instead of double-quote ''...''
- using equal signs, = and ==, versus !, !! for headings.