Following someone who follows you can be considered Hub-courtesy, but is not required for good Hub-etiquette. In my opinion following another author should only be done if you find their work interesting and as something you will read on a regular basis. If hubscore is of concern, following too many hubbers in a short period of time can actually lower your score, as it appears to be a little spammy.
Stick with following those who's work you enjoy, and feel honored that your followers find your work among their favorites.
I hope this helps!