404 Error clicking on a link to a deleted forum comment

Some users complaint, that they are getting a 404 error when clicking on links in their notification emails which should show new answers to their forum topics. We found out, that the content has been deleted in the meantime. Instead of a 404 error, we would have expected, that the user would see the deleted comment message instead in the forum thread.

Steps to reproduce:
- Create a forum topic
- write at least one answer/comment to it
- wait for the notification email
- delete the comment
- click on the link in your notification mail --> leads to a 404 error, but the "content has been deleted" message was expected. Most users also enter a reason why they deleted their content, so this message would be much more helpful for the user.
We don't want to have a common "the content has been deleted" message, we want the link to work also when the comment has been deleted. Because there is already a message. It would be really helpful for the user to see the deleted comment in the context of the original post to have the chance to read the original content.