Even though in the title, this FAQ talks about joining, in the body of the FAQ it mainly talks about watching. It might be good to change both the title and the text to include both.
In the title, "join" could become "join or watch."
In the body of the FAQ, here are replacements for the first two sentences (for the addition and for phrasing):
If you join a community or add it to your Friends list, that will not enable the members of the community to view your Friends-Only entries. The only people able to see your Friends-Only entries are those whom you list individually on your Friends list.