Bitbucket silently loses unsaved comments when browser window is closed

• SUMMARY
  stash silently loses unsaved comments when browser window is closed

• STEPS TO REPRODUCE
  1. Open a pull request
  2. Click on a diff line to add a comment
  3. Type some text but do not click on the "Comment" button
  4. Close the browser window

• RESULTS
  The window closes without complaining about the unsaved comment. The comment is now lost and I'm probably not even aware that it happened...

It would be nice to get some warning from the browser when about to close a window with unsaved changes to a form, for example.