RE: how to make a chatbot that gets annoyed at a user

You can do this with a Self script. You would need to check the difference between the current and previous input.

Something like,

if (Date.difference(conversation.input[-2].getCreationDate(), input.getCreationDate(), #millisecond) > 5000) {
    return "I'm glad your back, I thought you left.";
} else {
    return null;
}