I would like to inform you that the table resize feature in Firefox and IE comes from the browser and it is not implemented by the RadEditor control. You can find attached a simple editable iframe, with which you can examine the same results in the same browsers.
The only resize functionality, implemented in the RadEditor is the one provided under Chrome.
In IE, the resize handles appear only when the border of the table is selected. when the cross cursor appear. Please examine this screencast
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