My posts on this board vary from being completely serious to being completely unserious. I think it's easy to tell the difference.
If not, though, PROTIP: any moderator actions by myself, Morden, or Andrew are serious unless they involve attacking IE or FC boards with topic relocation, but that was just that one time
Also, any post I make that's more than, say, five sentences long is almost certainly serious because I have a tendancy to be very perfectionistic when I make the effort to do a big post
That's the same for many people here, I think it is pretty easy to tell when people on this forum are being serious, sarcastic, etc.