Alright, some more random thoughts on this topic.
I think one common theme you will see amongst introverts is control, specifically having control over your environment. The less control you have, the more uncomfortable it makes you feel. Go out with a small group of close friends, you can feel like you have control over the situation. However, as @kag123
stated, as the scale starts to tip in favor of strangers, your control and comfort slips.
had mentioned hosting parties at home. For me, home is my "safe" place. When we have company over, I am ok at first, but the longer they are there (regardless of whether or not I am having fun) it wears on me to the point where I almost feel trapped/overwhelmed as some of my control slips (don't mean to make it sound as dramatic as it may come across lol). Add in those family members who never want to leave, oh boy...
The funny thing is, I can be considered an extrovert, but once again, given the right environment. I go to a small local gym. Been going there when it opens (5am) pretty much every day for years. I see most of the same people there every day. I have zero issues striking up conversations, even with someone I may not know. The reason, this place has become a comfort zone where I have control over the environment. Send me to a big box gym and I probably just go about my business with my head down not speaking to anyone.
I wonder if for some who have issues with being in large crowds or noisy situations, it is in part due to a sensory problem with how we process all the extra "noise". I know the "noise" gets me overwhelmed very quick, and I am noticing the same behavior in one of my sons.
made a great post in regards to how some introverts can be perceived. I am sure at times I am perceived as being unfriendly, being snobbish, being a loner, simply because I am content being alone, lost in my own thoughts. The irony of it, I have no issues getting along with pretty much anyone, and for some reason people feel comfortable talking to me (which can be a bit of a cruel joke when you factor in how much I hate small talk lol).
The one time I am always an extrovert, when I am alone talking to myself, or when I find a killer MEME
The moral of the story, whether you are an extrovert or introvert, embrace it, be the person you want to be and f$ck anyone (umm, not literally...) who has a problem with this.