This line touches the topic (changes it's updated_at) when the topics/show action is hit. If you are like me and you're implementing fragment caching in your views and you are using the updated_at column to determine your cache_key, the cache will be invalidated on every request. I don't see any reason that it should touch the record.
I know the gem isn't really maintained at the moment, but I can create a PR to change this behavior if somebody with merge power can confirm the current behavior is not desired.
Thanks!! 😄