Last modified: 2009-07-19 14:21:20 UTC
As far as I can tell, we can currently only use the magic word DISPLAYTITLE in certain special cases, i.e. to change the case of the initial letter of the title, to add italics and bolding (maybe there are others). It seems to be impossible to use it to work around other technical restrictions on titles, such as the prohibitions on using certain characters. Surely this isn't necessary - just because there are technical problems with using a character in wikilinks, there should be no need to prevent it from being displayed to users in the article header.
See the note at http://www.mediawiki.org/wiki/Manual:$wgAllowDisplayTitle and http://www.mediawiki.org/wiki/Manual:$wgRestrictDisplayTitle .