You can be disciplined for what you post
Just about everyone today has some kind of social media account such as Facebook, Instagram, a personal blog or other online presence. There are limitations though on service members’ speech beyond limitations established over time by First Amendment jurisprudence. In other words, speech that is protected by the First Amendment in a civilian context may be prohibited in the Armed Forces when it undermines good order and discipline or discredits the military in some way. Limitations are often context-dependent.