Full disclosure: I am one of the developers on the aforementioned IRC server.

In a future release InspIRCd will adopt support for the server-time extension which will allow us to get rid of the timestamp duplication if a user's client supports it.

Interesting. Can you tell me what you think of Quassel as a protocol?

It's very specialized and last time I looked at it, it was based on Qt types and other ugly things. It would not be realistic as an alternative protocol for IRC itself.

Just a note that the QDataStream format is documented, and has been implemented in other languages such as Java. That doesn't mean that the Quassel protocol should replace IRC of course. :-)

Timestamps – there's a standard extension for this (see IRCv3 above). ZNC has been using it for maybe a year.

Senders – there's absolutely no reason to fake senders, since it was always valid for messages to come from people not in the channel.