If you send a mail with the plugin, this is added as a comment to the issue. It would be handy if there were a reply button somewhere if you open the comment. This way you don't need to add the recipient each time.
Further possible improvements:
add references to previous email: reply emails should be rendered in the email log with a reference to the original email log item
use message IDs or email headers to group related emails (maintain email conversation threads)
I think that reply link should be in email entry in email tab.
I agree, reply / reply all will be added to the Email log, not to the comment.
Released in version 6.3
Reply/Reply All is little bit confusing as it added to recipient user that initiated reply to instead of original sender and it should be excluded also in case if original sender is same sender as it is now. So I do not thinks so that should be included such users as they know that send it so no need for extra email.