`->text()` isn't safe to output as HTML. I'd suggest changing the `<em>$1</em>` in this message to `''$1''`, then using:
`$wgOut->addWikiMsg( 'editcount_refresh_time',  $currentWikiaMsg, $nextRefCurrW );`

Same below. Note as this is a subclass of SpecialPage, you can use `$this->getOutput()` instead of `$wgOut`, and `$this->getLanguage()` instead of `$wgLang` to avoid the globals.