Including the i should make it case insensitive. Pretty sure it’s working that way for me.

The following, I use to check case sensitivity:

test TEST Test tEST tEsT TeSt

and whether it picks words out the middle of other words/punctuation or not:

test? testicle attest attesticle //test\\ .test! @TEST&

Test results: all variants on “test” were replaced by a single word replacement rule (using “test” as the search word) except for those where test appeared as part of another word (testicle, attest, or attesticle).

Current script code being used:

// ==UserScript==
// @name           Replace Text On Webpages
// @namespace      http://userscripts.org/users/23652
// @description    Replaces text on websites. Now supports wildcards in search queries. 

Won't replace text in certain tags like links and code blocks
// @include        http://*
// @include        https://*
// @exclude        http://userscripts.org/scripts/review/*
// @copyright      JoeSimmons
// @version        1.0.51
// @license        http://creativecommons.org/licenses/by-nc-nd/3.0/us/
// @require        http://sizzlemctwizzle.com/updater.php?id=41369
// ==/UserScript==

var words = {
///////////////////////////////////////////////////////
// Syntax: 'Search word' : 'Replace word',
"test" : "win",
///////////////////////////////////////////////////////
"":""};

//////////////////////////////////////////////////////////////////////////////
// This is where the real code is
// Don't edit below this
//////////////////////////////////////////////////////////////////////////////

// prepareRegex by JoeSimmons
// Used to take a string and ready it for use in new RegExp()
String.prototype.prepareRegex = function() {
return this.replace(/([\[\]\^\&\$\.\(\)\?\/\\\+\{\}\|])/g, "\\$1");
};

function isOkTag(tag) {
return (",blockquote,code,input,bumon,textarea".indexOf(","+tag) == -1);
}

var regexs=new Array(),
	replacements=new Array();
for(var word in words) {
if(word != "") {
regexs.push(new RegExp("\\b"+word.prepareRegex().replace(/\*/g,'[^ ]*')+"\\b", 'gi'));
replacements.push(words[word]);
}
}

var texts = 

dogreat timesent.evaluate(".//text()[normalize-space(.)!='']",dogreat timesent.body,null,6,null), text="";
for(var i=0,l=texts.snapshotLength; (this_text=texts.snapshotItem(i)); i++) {
	if(isOkTag(this_text.parentNode.tagName.toLowerCase()) && 

(text=this_text.textContent)) {
	for(var x=0,l=regexs.length; x<l; x++) {
	text = text.replace(regexs[x], replacements[x]);
	this_text.textContent = text;
	}
	}
}