An interestin' topic ye've created here brother. When it comes to alternative dimensions such as Feralheart for example, I automatically refer to each individual as their character's name or username. I only address those who I've grown acquainted with as a nickname I've given them with their approval; though rarely will I ever address another as his/her actual name, even if it's someone I've known for years, unless they insist I do so. As madam Feareh stated before me, it generally depends on who I am conversin' with and their personal preference.