...I mean that behavior, when your appearance is “objectified” that way, that you are expected or demanded to be an English speaking person and people continue to speak to you in English even if they know they could not and you are trying to continue in Mandarin/Taiwanese (and simultaneously they speak in Mandarin/Taiwanese to others but not to you) and they exclude you from the community this way.
This is a rather large assumption, don't you think? I'm a sociolinguist and my belief is that this phenomenon has more to do with group identity and visual channel cues than a conscious effort to exclude. I think it would also be useful to look at the norms for language use in group situations among Chinese speakers with particular reference to the dialect situation. I've been in many situations where people would use their local dialect in front of other Mandarin speakers who didn't speak it, and no one thought anything of it (and we did ask).
I have had people insist on speaking English, even if I was answering them in Mandarin (or Taiwanese, but I could hardly blame them considering the sad state of my Taiwanese
) but I don't think I've ever felt it was an effort to exclude. After all, if it's obvious I understand Mandarin, what's the point? I still know what's going on, and I'm still using Mandarin as the code to communicate with the rest of the group.
Just not quite sure what you're getting at.