Using GIF image in the RadEditor to resize them or manipulate them somehow and saving them, results to a GIF file with black background.

You can safely use PNG images when transparency is needed, which are fully supported. 

As a workaround use the overload method Dock(String zoneID):

RadDock1.Dock(RadDockZone1.ClientID);

In IE the command works fine.

In FF the command is always disabled.

In Chrome is always enabled, but using it do not affect the content.

If you need this tool to be always disabled under Chrome, you can use the following approach to disable the tool:

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

<script type="text/javascript">
	function OnClientSelectionChange(sender, args) {
		if ($telerik.isChrome) {
			setTimeout(function () {
				sender.get_toolAdapter().getToolByName("AbsolutePosition").set_enabled(false);
			},0)
		}
	}
</script>

The encountered issue stems due to inheritance of CSS rules that select globally table elements. 

For the time being you can use the following CSS reset to improve the layout of the Editor's table elements:

.reLayoutWrapper, .reWrapper_corner, .reWrapper_center,
.reLeftVerticalSide, .reRightVerticalSide,
.reTlbVertical, .reToolCell, .reContentCell,
.reToolZone, .reBottomTable, .reEditorModesCell,
.reBottomZone, .reResizeCell {
	border: 0 none !important;
	padding: 0 !important;
}

.Telerik.reWrapper, .Telerik.RadEditor .reContentCell,
.Telerik.reColorPicker, .Telerik.reInsertTable,
.Telerik.reCustomLinks a:hover {
	border: 1px solid #828282 !important;
}

.reLeftVerticalSide, .reRightVerticalSide {
	padding: 1px !important;
}

Note that these CSS rules will affect RadEditor controls outside the RadGrid. If you need to modify only RadEditors inside RadGrid, use CssClass property and change the CSS selectors according the set class name.

Also, upon the used color you may need to change the border-color according to the Skin design.

With the support of insert list command in Track Changes functionality, users can insert lists. Although with enabled tracking users are not able to delete the list items, but only the text inside.

Steps to reproduce:
http://demos.telerik.com/aspnet-ajax/editor/examples/trackchanges/defaultcs.aspx

1. Insert a list with enabled TrackChanges
2. Start deleting list items

Expected: The whole list item is removed
Actual: Only the text inside the list item is deleted

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