Feature request: ability remove specific messages from chat

[ian-kelling]

/clear is useful for removing offensive messages from chat, but it
would be nice for operators to have the ability to remove specific
messages as the rest would be useful.

[jech]

Right. That will require a protocol change (we'll need to add a unique id to all chat messages), so it's not going to happen in the 0.8 branch, and perhaps not in 0.9 (which is pretty much in feature-freeze).