Example for proper text replacement.

ext.narayam.js.patch

--- Base (BASE)
+++ Locally Modified (Based On LOCAL)
@@ -150,7 +150,54 @@
 			$element.removeClass( 'narayam-input' );
 		}
 	}
+		/**
+		 * from: http://stackoverflow.com/questions/3274843/get-caret-position-in-textarea-ie
+		 */
+		function offsetToRangeCharacterMove(el, offset) {
+			return offset - (el.value.slice(0, offset).split("\r\n").length - 1);
+		}
+		/**
+		 * IE part from: http://stackoverflow.com/questions/3274843/get-caret-position-in-textarea-ie
+		 */
+		function setCaretPosition (el, iCaretPos)
+		{
+			if (document.selection) // IE
+			{
+				endOffset = startOffset=iCaretPos;
+				var range = el.createTextRange();
+				var startCharMove = offsetToRangeCharacterMove(el, startOffset);
+				range.collapse(true);
+				if (startOffset == endOffset) {
+					range.move("character", startCharMove);
+				} else {
+					range.moveEnd("character", offsetToRangeCharacterMove(el, endOffset));
+					range.moveStart("character", startCharMove);
+				}
+				range.select();
+			}
+			else if (el.selectionStart || el.selectionStart == '0') // Firefox
+			{
+				el.setSelectionRange(iCaretPos, iCaretPos)
+			}
+		}
 	
+		function replaceAt( $element, start, end, replacement )
+		{
+			var newCaretPosition;
+			var text = $element.val();
+			if ( text.length == 0 ) {
+				$element.val( replacement );
+				newCaretPosition = replacement.length;
+			} else {
+				var firstString = text.substring( 0, start );
+				var lastString = text.substring( end, text.length );
+				$element.val( firstString + replacement + lastString );
+				newCaretPosition = firstString.length + replacement.length;
+			}
+
+			setCaretPosition($element.get(0), newCaretPosition);
+		}
+	
 	/**
 	 * Keydown event handler. Handles shortcut key presses
 	 * @param e Event object
@@ -224,15 +271,7 @@
 		replacement = replacement.substring( divergingPos );
 		
 		// Select and replace the text
-		$this.textSelection( 'setSelection', {
-			'start': startPos - input.length + 1,
-			'end': endPos
-		} );
-		$this.textSelection( 'encapsulateSelection', {
-			'peri': replacement,
-			'replace': true,
-			'selectPeri': false
-		} );
+			replaceAt($this, startPos- input.length + 1, endPos, replacement);
 		
 		e.stopPropagation();
 		return false;