It's good to add addtopic "new topic" when dialogue is supposed to add a new topic. Sometimes new topics aren't hyperlinked when another mod's topic includes the same words, so they don't get added.

Example the sentence should link this topic
I would have you deliver a message to Port Telvannis.
but another mod could be adding the topic deliver a message. Even if the npc who speaks the first line would never have that other topic, the engine checks if it's available and that can be enough not to link the intended topic.