Selectable Text in Textbox Visual

For one, this is an accessibility issue - People may wish to select text to help them read, or direct a screen reader to it. For another, this is basic usability - it's user expectation that text is selectable. And finally - there are plenty of reasons to direct users to select the text. I'm currently developing a new page, which requires discussing with users exactly which principles need to be used. I've got a text box with commentary, and the sensible thing would be to let them copy some values from there and paste them to a text filter so they can review these cases and come to a conclusion on the best way forward. But since the text box blocks any kind of user interaction, it's far clunkier than it needs to be.