Empathy does not behave correctly when connected to IRC channels with special characters in their name. When joining a channel with an exclamation mark in it's name (for instance), empathy is unable to send messages to the channel.
If you join channels Hello!123 and Hello!123! empathy receives messages from both channels in the same chat window, but again it is still unable to send messages to either channel. No messages appear in terminal when empathy is run from there.