I think it would be useful if topics came with some more information, perhaps a short blurb describing what the topic is about, what is or isn't within the scope of the topic, etc.
Obviously, there are many topics that are self-explanatory, so this description could be optional. For example, I'd expect that everyone knows what the topic Star Trek is about, and that it shouldn't be used to discuss the latest Star Wars movie, or something else altogether. However, there are topics where this isn't the case.
Example 1: When I joined, one of the first few topics I followed was "photography". I expected this topic to contain conversations about photography - what gear (or camera settings) to use, how to get the best shot in mediocre lighting situations, how to post-process, that sort of stuff. What I got instead was (mostly) random image shares without much of a discussion, so I eventually unfollowed that topic.
It doesn't really matter if it's me or the others who misinterpreted the topic - but obviously, there was some misunderstanding going on. Some descriptive text might have helped both of us.
Another thing I'd like to see is an option to flag a conversation if we think that it doesn't belong into one or another topic. We already can flag conversations, but are then asked why we "think this content doesn't belong on Cake". In many cases, I do not think that content needs to be removed altogether - but would still like to see it removed from a topic that I follow for completely different content.
Example 2: Another topic I followed after joining is "Google+". Similar to my above example of a "Star Trek" topic, I'd expect this topic to be understood even without a description, and I'd expect to mostly see conversations about this specific software product and/or platform: what worked, what didn't, where did it all go wrong... Yet, what I mostly see in that topic are conversations that just happen to be started between former Google+ users (or not even that).
Here, being able to somehow state that "I don't think this conversation belongs here" would help - both me, if it leads to less off-topic conversations in my feeds, and the moderation team (and thus the platform as a whole), who can't possibly know everything about every topic.
Last but not least, and I think I've brought this up before, if this platform grows there will be a time where it will no longer be possible to confirm each and every conversation "in-house". At that point, it would be great to have functionality ready that allows others (long-term members who have shown themselves to be both well-behaved in general and knowledgeable about a certain topic) to help with the moderation.
I'm neither asking for the proverbial keys to the platform, nor am I volunteering as an unpaid moderator for all the topics. What I'm suggesting is more like being recognized for being a regular contributor to some topics, so that my flagging actions in regards to that topic (if they happen) are given more weight in some moderator's priority queue.