Being SEO friendly doesn't require installing a plugin by definition, some web applications are actually good at it out of the box. I think MediaWiki is one of them :)
I am not sure if i can confirm this. I did post a short text into a Wordpress installation with a SEO Tool and landed on No.1 on Google
The same Text with same header, I did write into a Mediawiki installation and its not listes on the 1st 10 pages in google.