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They share the same role: to show topics. Yet, they are using very different templates. Maybe they should share a common "topicList" template?

Yep.
I think I started working towards sharing the same code (both for the template and the "source", technically, the only difference between the two pages is just how the listing is retrieved), it should be up at github in one of the branches (not sure which one), even though recently I realized there is a better way to do it than what I did so far.