It depends who I'm talking to, and the context I use it in. For example, if GNTLGNT made a post saying he was upset about something and wanted support I would likely refer to him as Scott when replying as it would seem more personal. The more you talk with someone and become friends you will likely discover whether they are okay with their proper name being used on the main board.
Also, there's members here I use pet names with or even multiple names, eg; Ms Mod, Marsha, Modster, Motherator, Maaasha...it just depends what mood I'm in.
So no one ever refers to her as "Marsha, Marsha, Marsha"? - not sure if you guys got the Brady Bunch over there but it was a popular show here on the telly.