In the daily summary I don't have a link to reply to a post. In fact, I don't even have the text of the posts, just the titles with a link to the server.
I've just changed the options to full digest (but it's limited to 12 messages). I'll check tomorrow if I have the option to reply.
In any case, a lot of people currently uses the daily summary at JG that features all the messages of the day in just one mail. I think that the daily summary option will be widely chosen and people will get confused by not having the messages directly on their mail and no option to reply.
On the other side, I've tried to create a new post directly from my mail and also tried to reply a previous one but changing the subject to a specific topic and removing the full contents of the previous post.
In both cases I've got a Failure Message :
500: You have replied to a digest message, which is not permitted. Please click on the 'Reply to this message' link under the message you'd like to reply to, and you will be taken to a page to enter your reply.
So there's no possibility to create new posts or reply to messages by replying directly to a mail.