If you are interested in maintaining your privacy on a public forum, use a pseudonym (for example, amazingly, Flying Monkey is not actually my real name!*) and not the same pseudonym as you use on any other forum you frequent, don't use a personal photo, and do not put (accurate) personal information in your profile etc...
*Personally I don't care that much, I've just always been Flying Monkey on cycling forums, and a few people know who I am IRL, although interestingly, data aggregators don't seem to have made the connection...