I just signed up for an account on Ask Different. After some time, I noticed that Ask Different got automatically added to my personalized list of Communities in the site switcher.
As I had personalized the list, there shouldn't be any automated changes taking place.
This is getting very annoying. I have been looking at some sites which I reached via the Hot Network Questions. Some of the content is interesting/good and I want to vote/comment. To do that I need to create an account (which happens fairly frequently). As soon as I do that, the site gets added to my manually created list.