Shoutbox

Although it is correct that not all clients are able to recieve offline messages, people with MSN Messenger 7.5 or higher can read them. And that is the majority of all.

Together with this, the offline messaging and Plus!'s old comeback-message are extremely similar (though there are indeed differences).

Since offline messages became available, only one or two requests have been made to bring back the comeback-messages (and I know one of those requestors was very satisfied to discover the offline message system from Messenger itself; he didn't knew it existed)

And to add to this: a comeback-system like the one in Plus! 3 is extremely very easy and short to make with a script.

So putting everything together, I don't think it justifies it to add this back. There are, IMHO, more important and much more requested things to bring back (eg: custom names with (!N) support).

Thus, a script is the best solution...

I'm not against bringing it back though... but I know I wont use it anymore (and if I need something to send to someone while we both are online, I either make a notification or either make a script with a few lines of code to do it)

But that's just my personal opinion.