You are using the wrong hook name
action:composer.topics.post => for new topic
action:composer.posts.reply => for new reply
Whoa, that is a nice theme. Upon inspection of the source, it looks like that homepage is from the custom-homepage plugin, the topics list and categories list are both widgets, with some custom css applied. So, if you wanted to use theme-exodo, that's how you would achieve that effect.
With official themes you will be thinking of any theme the NodeBB team puts out. Primary Persona at the moment.