1. If you reopen an issue you only see some properties of the issue - but you do neither see the summary nor the description nor any comment. Summary and description and all comments should be available when reopening an issue so you can read old text and can refer back (as it is when adding a new comment).
2. In addition, when closing an issue, you do not see the description of the issue you are closing, so the possiblity of closing the wrong issue is high, it is only a big deal when it comes to reporting, as all reopens are seen as development failures to managment.
Major from usability point of view.