The opening scene where the vets in the hospital are talking was totally unscripted. They were real Vietnam vets discussing their own views about the war. Jon Voight was supposed to have added to the dialog, but out of respect stayed silent and listened.
Jon Voight's role of Luke Martin was loosely inspired by paralyzed Vietnam veteran Ron Kovic, who was making inroads in Hollywood with his book "Born on the Fourth of July" at the time. Of course, Kovic's book and story was in 1989 put on the screen with Tom Cruise in the role of Kovic.
One of the first films even partially dealing openly with the idea of sex between an able-bodied person and a disabled one. Other films dealing with disability and romance had indirectly implied it or avoided it altogether (such as in The Best Years of Our Lives (1946)).
In the documentary This Film Is Not Yet Rated (2006), this movie was used as an example of how much more strict the MPAA had become with regards to the sexual content of movies since the 1970s. It was noted that Coming Home got an R rating despite a long scene where a woman reaches an orgasm from oral sex, whereas similar scenes made in the 90s and 00s gave their respective movies (especially _Boys Don't Cry (1999) and The Cooler (2003)) an initial NC-17 rating.