There is a mismatch between Closing an Epic and marking it as Done.
In my opinion either of the two should automatically do the other.

I can't mark a Closed Epic as Done anymore, since our Closed issues are read-only. This means I have to reopen (Issue View) -> mark as done (Agile View) -> close (Issue View). This is not very user-friendly and people tend to forget to Mark as Done anyway.

After I Mark as Done, the Epic no longer shows up in the Epic lists, so if it isn't Closed automatically, these issues are difficult to track down. They will show up in simple open/closed statistics, skewing results.