The reason why, GS, is that it pushes their buttons. What if you were a declared atheist? What if you had begun your statement with "I am an atheist..." Well, then it would push a different set of buttons, and a different bunch of people would be bothered by it.

As an atheist you could end each post with:

"I'd say 'blessed be', but it wouldn't make any difference, because there's nothing out there to bless you, so I won't. I'd say 'good luck', but I don't believe in luck either. I'd say 'see ya later'...but maybe I won't, so I can't say that because it might prove false. Hmmm. Aw, just forget it!"

That would probably bug certain people too, specially if it was after every single post. I say, stick with "Be Blessed". It's short, friendly, and easy to type (even if it isn't easy to say ten times in a row really fast).