I respectfully disagree for the large part. My own brain seems to have no issue coupling functionality to visual design. Yes it's probably less optimal for novice-to-expert transition than having colour variants, but conversely it also gives stronger immediate affordance as to what subreddit you're using..
It might depend on one's browsing habits. True, I believe the intention was to give subs their own identity, as if they were individual websites. However, I frequently click between subs. The fact is that it's a single website.
I have no question that every study of user interface ever published would indicate that buttons changing visual appearance, position, or availability with no predictability several times in a browsing session is a high friction interface.
