How to reproduce:

• Have issue or PR page opened
• Somebody writes comment, it gets shown dynamically without page reload
• Click on "Reply" button
• Popup with "Failed to retrieve comment text" appears, you need to reload the page use the reply button (that one which quotes the comment you're replying to)

Tested with Google Chrome on pagure.io . I have uBlock Origin installed but it's not blocking anything on pagure.