Version:           3.5.5 (using 3.5.5, Debian Package 4:3.5.5a.dfsg.1-8etch1 (4.0))
Compiler:          Target: i486-linux-gnu
OS:                Linux (i686) release 2.6.18-6-686

Just as I am used to use regex search & replace in kwrite, kate etc., for a search within the textarea box I entered the regex to find ("= (.+) ="), ticked "[x] regular expression", entered the replace phrase (" \1 "), and ticked "[x] use placeholder".

In kwrite, this settings -- for a snippet of mediawiki markup -- cause the marked up headlines to become one level lighter. Unfortunately, in konqueror's regex search & replace, I get the patterns found, but the replace doesn't work: Everywhere I get a pattern found, the replace is just a plain " \1 ".

And, yes, the "[x] use placeholders" is really ticked.