Like I said above it's a public forum, not someone's living room, I don't really think it's acceptable as you don't know whether the person coming out with the banter is racist or not.
raises an interesting question on defintion – is racism in the eye of the beholder or the speaker?* It reworks the same discussion about taking offence (not just in a racist context): is offence given or taken and if the latter is it the fault of the giver if offence was not intentionally given? (if you get my point)
Interesting indeed. For me something on here can be racist independently of intent. It's not about offence and that ios different because it is entirely subjective, however racism is pretty clear to spot, for some of us at least.
Oh and uplink's joke is about how Chinese folk speak english, it's perhaps borderline racist as it's not directly derogatory. I wouldn't tell it for that reason as well the fact that it's not that funny.