Selected text can be removed in some cases when focus is lost and then regained. This can be reproduced on Linux and Mac (it does not happen on Windows).

Linux:
Run any application with any of mentioned Text edit control and any other control.
Select some text into Text* control, and click on another control.

Selected text in Text* is removed.


Mac:
Run any application with TextArea and any other control.
Select some text in TextArea control, and click on another control, then click on TextArea again.

Selected text in TextArea is removed.