Shoutbox

It's enough pain in the ass to see KeyStorm {in bed} (Away) when you don't have Plus! installed, so it would be even worse if there was also a tag prepended to the nickname. This, also, would screw up alphabetic sorting a bit more (format nicknames already does).

I've always supported Plus! Detection. And there are several ways to make a legal detection possible (one of them making a big prompt during installation with no default choice, like in the adware license). Once bypassed this privacy issue, there's lots of ways to make Plus! be recognised and tracked. As it was suggested before, the first nickname sent to a contact in a conversation (conversation nickname is different to the contact list nickname and is internally independent, like proved by Stuffplug and in the same way your personal status tag does not appear in conversations) a similar tag along appended to the nickname and that would be checked by the other Plus!. This would be a subtile and still effective way to have acknowledge the presence of Plus! in the remote contact machine.

And yes, that would make the user experience even better. It would tell the user when certain features are used that they may not work if the contact has still not sent such a Plus! identificator. Now custom sounds have come this makes more sense. Non-Plus! users get to see the ugly sound-ID, as well as all format characters in a nickname and in the text.

However, Patchou is not willing to do this for some reasons I can't seem to understand, because all contras are beaten by all the pro's and still there is no real violation. We can remember that every Plus sends by default user statistics to the server, and it isn't much of a matter someone telling their contacts that they have Plus! installed.
Even worse, it's always a pain to have to ask whether the contact has Plus! or not before you send a custom sound.

My 2 cents.