I have no particular objections to having an option for hiding the arrow (not that it's one I'll be using), but I do find that menu really useful, so would rather it not get deleted altogether for everyone

That arrow is incredibly useful. It takes up only a tiny drop of space (since it has not text, just an icon) and avoids having to scroll down to navigate to other communities. Is it superfluous - Yes. But that is (for better or worse) the nature of modern user interfaces - e.g., to print in a typical application you will have a menu selection (File->Print), a printer icon and Control-P - and sometimes a Print button inside a web page or other application as well - all to do the same thing.

Maybe it would be a good idea to have the possibility to customize it so that only the communities you are interested in appear?

@Lundin, and similarly the dashboard.