Be careful about online identity, and keep a distinction between things that are public and private, work-related and friend-only appropriate. When you leave Princeton, you are going to lose the ability to edit things you posted in a course blog. You might have very different opinions twenty years from now then you did when you were a Princeton student.
Although you log into the WordPress blogs at Princeton using your LDAP credentials, you need not display your real name to readers of your blog. Your WordPress profile (under your name in the top grey bar when you are logged into WordPress) contains a field called “nickname.” This will be the author name that is displayed on posts and pages that you write. You can use any alias you want, or use your real name.
FERPA stands for “Family Education Rights to Privacy Act.” It requires educational institutions to protect the privacy of students. Classroom discussions are meant to be private. Because of this, we try not to make it obvious who is enrolled in a specific course during a semester. You are not obliged to reveal your identity and should not ever explicitly reveal the identity of others in your class. Revealing your own identity is your decision.