Your English looks superb to me, but I’d like to point out one typo, so that you can correct it:
“Trusting native speakers TO always TO give you the right answer is also bound to create problems.”

Living in the North i.e. in the heartland of supposed “standard” Mandarin Chinese makes one even more likely to take taxi drivers and random university classmates as authorities on their language.

Excellent comment! It’s also the case that many people in the north (read: Beijing) don’t know the difference between standard 普通話 and 北京話, thinking that they are one and the same. For example, I’m currently taking a phonology research course with a teacher who has worked as an examiner for the pronunciation exams taken by teachers, news anchors and so on. She said that some Beijingers have the attitude that “I’m from Beijing, therefore everything I say is 100% standard and correct”. Making oneself the reference point for what is correct is ignorant and a bit arrogant (and it would be so in any other language as well). It also makes it hard for some people to understand why they fail the exam even though they supposedly speak perfect standardised Chinese.

After having taken linguistics courses with mostly native speakers as classmates, it’s also striking how different their intuition for the language is. It’s not uncommon for half the class to approve of one way of saying something and the other disapproving of the same sentence (obviously, only tricky cases are dealt with in this way, but they are too common to make me comfortable).

My own experience was different. I learned Chinese in Nanjing and Suzhou where the many Wu dialect(s) are the language of everyday communication. Even as an upper-intermediate speaker living in Jiangsu I know in talking to my girlfriend’s 83 year old grandmother who uses literally two verbs for everything (搞 and 弄) when she speaks Putonghua, says 跑 to mean 去, asks me if I’d like to 吃茶 when I come over, and frequently asks my girlfriend or her mother or even me occasionally how to say the name of a fish or a vegetable in Mandarin, that I can’t go to her for the proper use of 尽管. This has absolutely nothing to do with intelligence or cultured-ness. She simply never, ever speaks Putonghua in her daily life. I am literally the only person she speaks it with.

In short I think one can be disabused of the idea that native speakers know everything much more quickly if one studies in the South, or in East Central China or in Western China, or really anywhere other than Harbin, Beijing, Jinan, Tianjin etc… and even in those cities one should be hearing enough Jinan hua or Tianjin hua to realize that “native speaker of Mandarin” often translates to “native speaker of a local dialect, trained speaker of standard Mandarin” for a lot of the people you are going to run into at the pool hall or the basketball court. This is not to say that Mandarin speakers in non-standard dialect-regions are incapable of speaking excellent Putonghua. In fact my current teacher walks into class most days talking loudly in Chongqing hua on her phone and then promptly switches to flawless Putonghua as soon as class begins. It’s a skill she has acquired though, not something heaven-sent or as we‘ve learned to say in Chinese “天生的.”

That’s a really neat way of putting it, I’ll remember than and use it next time I run into this kind of situation. Thanks for sharing!

It’s worth remembering something a good friend of mine said years ago: “We’re all learners, but some of us started learning earlier.”

That hits the nail on the head! No-one pops out of the womb with the capacity to hold a conversation, and in fact it takes years full of many errors for any so-called native speaker to reach the level of holding a very simple conversation.