Tangent: Texting has an inherently more personal feel (at least to me, your experience could be different obviously); when I get a text, I feel much more inclined to immediately respond than I would with an email, because that's just the stigma it has.

Main point: I'd argue that "online" and "typing" statuses are just ways to make texting more convenient. If you don't like the "texting v. email" comparison I can just rephrase it, they want chat to better connect users; rather than feel like you're talking to "a moderator" or "that one frequent poster" chat with statuses reminds you that you're talking to a person. Not a total fan of the personal aspect to it, as that's very Facebook-esque like you said, but making something more convenient should always be the goal.

But, what you described is less convenient for me, not more. I don't want to be pressured to immediately respond.