Here are the steps to reproduce the behavior:
1) Go to one of your demo page: http://demos.telerik.com/aspnet-ajax/editor/examples/xhtmlvalidatortrackchangesformatcodeblockdialogs/defaultcs.aspx
2) Go to Html mode and delete everything. Go back to the design mode.
3) In the design mode, type a word. Double click the word to select. Delete the word.
4) Type another word. Double click to select. Then click the insert link button.
5) Note that the Link Text line is disappeared in the insert link dialog.
See attached screen shot.
1) Go to one of your demo page: http://demos.telerik.com/aspnet-ajax/editor/examples/xhtmlvalidatortrackchangesformatcodeblockdialogs/defaultcs.aspx
2) Go to Html mode and delete everything. Go back to the design mode.
3) In the design mode, type a word. Double click the word to select. Delete the word.
4) Type another word. Double click to select. Then click the insert link button.
5) Note that the Link Text line is disappeared in the insert link dialog.
See attached screen shot.