When only one word is inside the content of the editor. If you select it and try to apply a desired class name from the mentioned tool, nothing happens. 

In scenarios where RadEditor is moved through the DOM the typical approach is to call the onParentNodeChanged method in order to re-render the editor. In Edge browser this does not work. CleanAtributes filter is alerted as failed and further RadEditor is unresponsive. 

Temporary solution is to switch the content area mode to DIV:

     <telerik:RadEditor ID="RadEditor1" runat="server" ContentAreaMode="Div" />

Using the delete key in the content area of the RadEditor sometimes cause incorrect behavior to be encountered, e.g., content disappearance, incorrect elements to be removed etc.

For example pressing delete key before a list element, the li tag is removed, instead of just the cursor to be positioned in it.

This behavior comes from the browser and there is no RadEditor logic that interferes with it.

It would be nice if this inconsistencies are handled via custom commands that act more stable across browsers. 

The following issues are fixed with this item:

Pressing backspace in a table sometimes inserts non breaking spaces
Could not complete the operation due to error 800a025e when deleting table columns
Redundand nbsps are added to the content using backspace inside <ul> in IE9
IE10 crashes when nested lists are highlighted and deleted
Incorrect List nesting is generated when a Paragraph is deleted via backspace key under IE11

You can workaround this issue by using this override:

<telerik:RadEditor runat="server" ID="RadEditor1">
    <Content>
        <br/>
        <iframe src="about:blank">Iframe not supported</iframe>
    </Content>
</telerik:RadEditor>

<script>
    Telerik.Web.UI.Editor.Utils._copyElementsBetweenNodes = function (oldNode, newNode, elementName)
    {
        var oldElements = oldNode.getElementsByTagName(elementName);
        var newElements = newNode.getElementsByTagName(elementName);
        for (var i = 0; i < oldElements.length; i++)
        {
            switch (elementName)
            {
                case "script":
                case "title":
                    newElements[i].text = oldElements[i].text;
                    break;
                case "style":
                    if (newElements[i].innerHTML != oldElements[i].innerHTML)
                    {
                        newElements[i].styleSheet.cssText = oldElements[i].styleSheet.cssText;
                    }
                    break;
                case "select":
                    newElements[i].selectedIndex = oldElements[i].selectedIndex;
                    break;
                case "input":
                    if ((oldElements[i].type == 'radio' || oldElements[i].type == 'checkbox') && $telerik.$(oldElements[i]).attr("checked"))
                    {
                        $telerik.$(newElements[i]).attr("checked", "checked");
                        if ($telerik.isIE9Mode && oldElements[i].type == 'checkbox' && oldElements[i].checked)
                        {
                            newElements[i].checked = true;
                            newElements[i].setAttribute("checked", "checked");
                        }
                    }
                    break;
                case "iframe":
                    var innerHTML = oldElements[i].innerHTML;
                    if (innerHTML)
                    {
                        var outerHTML = newElements[i].outerHTML;
                        if (outerHTML)
                        {
                            var gtIndex = outerHTML.indexOf(">");
                            if (gtIndex > 0)
                            {
                                outerHTML = outerHTML.substr(0, gtIndex) + ">" + innerHTML + outerHTML.substr(gtIndex + 1 + innerHTML.length);
                                newElements[i].outerHTML = outerHTML;
                            }
                        }
                    }
                    break;
                default:
                    if (newElements[i].innerHTML != oldElements[i].innerHTML)
                        $E.Utils.setElementInnerHtml(newElements[i], oldElements[i].innerHTML);
                    break;
            }
        }
    };
</script>

Inserting an image after opening ImageManager from within the ImageManager's Properties tab throws JS error. The issue is reproducible both in IE and Firefox

video: http://screencast.com/t/n4T0XYtSpt

For example, using this markup:

<telerik:RadEditor ID="RadEditor1" runat="server" ToolbarMode="RibbonBar">
</telerik:RadEditor>

and this Page_Init code:

protected void Page_Init(object sender, EventArgs e)
{
    RadEditor1.RenderMode = RenderMode.Lightweight;
}

Causes icons to either miss or their position is incorrect.

Instead of null, the String.Empty can be used. 

When user has changed image properties via Image Properties dialog, changes are getting cleared when area is being added via Image Map Editor. 

For the time being you can disable the StripCssExpressions  filter:
    protected void Page_Load(object sender, EventArgs e)
    {
		RadEditor1.DisableFilter(Telerik.Web.UI.EditorFilters.StripCssExpressions);
    }

Alternative approach to fix the issue is removing the StripCssExpressions filter from the client-side filters collection, so that the server-side functionality could still sanitize the HTML content:

<telerik:RadEditor runat="server" ID="RadEditor1" OnClientInit="OnClientInit">
	
</telerik:RadEditor>

<script type="text/javascript">
	function OnClientInit(sender, args) {
		sender.set_contentFilters(sender.get_contentFilters() - Telerik.Web.UI.EditorFilters.StripCssExpressions);
	}
</script>

When the EnableTrackCahnges functionality of the Editor is set to true, a context menu is shown only if the user right-clicks over a tracked change. Clicking over a not changed element does not pop-up any context menu (neither the Editor's not the browser one). The issue is reproducible in all browsers.

Steps to reproduce:
1. Run the following configuration:

            <telerik:RadEditor ID="RadEditor1" runat="server" EnableTrackChanges="True">
                <Content>
                    <span>SPAN dssad</span>
                    <div>DIV fsdfksjdfkf</div>
                    <p>Paragraph jfdshfksjdhfksdhk</p>
                </Content>
            </telerik:RadEditor>

2. Right-click over a not track-changed element.

Actual result: No context menu is shown.

Expected result: The Editor's default content menu (or the browser on) is shown.

When a tool has a longer name, part of the text drops to a new line, and causes incorrect layout. 

To resolve you can use the following CSS rule:

.reDropDownBody a.reTool.reToolText {
    white-space: nowrap;
}

When pasting list items over an existing one, the list from the clipboard is added to new UL element. The proper behavior it should be to paste the existing content and adapt it to the existing list.

When EnableTrackChanges property of RadEditor is set to true:

-The font name of the written text in RadEditor cannot be change and instead the default one is used. This behavior is observed under FireFox, Chrome and Safari. The workaround is to mark the already written text and then set the desired font.

-The chosen font size from the toolbar returns to its default value when the cursor changes its position and then returns back to its previous position. This behavior is observed under FireFox.