Just throwing in my $0.02, but I rather like these markers. I have to modify my typing in GChat a bit to get them working right, but I often find myself longing for -strike- when typing, for irony's sake.

It'd be nice to turn it off for those who take issue, but there's definitely a contingent of people who rather like it, as well. I find it odd there's no labs feature to turn off/expand the markup.