As an official side note, there will be abilities, powers, etc… that will allow a player to alter their shape, appearance, state of visibility, tangibility, and all that. I do think it would be easier for someone to put a symbol or notation before their play to signify this rather than get into an argument because someone missed their line about being in some state. It's probably going to be easier to establish this change now, while we are earlier on than to have to later as new powers, skills, and abilities come out I think.
Of course, this comes from the idea that it's a lot easier to notice a symbol in front of someone's RP rather than the text of it. I look for location markers before anything to see if I even need to pay attention to the RP.
Ideas for State Markers:
[*] Spirit World