The issue can be workarounded by calling preventDefault of the mousedown event when ComboBox item is clicked:
<telerik:RadScriptManager runat="server" />
<script>
	var onDocumentClick = Telerik.Web.UI.RadComboBox.prototype._onDocumentClick;
	Telerik.Web.UI.RadComboBox.prototype._onDocumentClick = function (e) {
		if (!e) e = event;

		var target = e.target || e.srcElement;

		while (target.nodeType !== 9) {
			if (!target.parentNode || target == this.get_element() || target == this.get_dropDownElement()) {
				e.preventDefault();
				return;
			}

			target = target.parentNode;
		}
		onDocumentClick.call(this, e);
	};
</script>

<telerik:RadComboBox ID="RadComboBox1" runat="server" RenderMode="Lightweight" OnClientBlur="OnClientBlur"
	CheckBoxes="true">
	<Items>
		<telerik:RadComboBoxItem Text="Item1" Value="1" />
		<telerik:RadComboBoxItem Text="Item2" Value="2" />
		<telerik:RadComboBoxItem Text="Item3" Value="3" />
		<telerik:RadComboBoxItem Text="Item4" Value="4" />
	</Items>
</telerik:RadComboBox>

<script>
	function OnClientBlur(sender, args) {
		console.log("Blur event");
	}
</script>

A workaround is to add the settings in the markup, for example:

<telerik:RadPersistenceManager runat="server" ID="RadPersistenceManager1">
	<PersistenceSettings>
		<telerik:PersistenceSetting ControlID="RadTileList1" />
	</PersistenceSettings>
</telerik:RadPersistenceManager>
<telerik:RadTileList runat="server" ID="RadTileList1">
</telerik:RadTileList>

Adding CSS styles for the table layout via the TableCssLayoutTemplates adds the style element inside the body, which is non W3C compliant content.

Under IE10 and 11 the CrossFade animation causes a random flickering. 

The long code lines in the QSF code viewer are very hard to read as the only way to get the horizontal scroll-bar is to reach the bottom of the page.