Microaggressions are a real and valid concept. The issue in most of these cases people are telling is that the people accusing each of you of microagressions are using the term incorrectly. I will explain.
According to Oxford Languages, a "microaggression" is "a statement, action, or incident regarded as an instance of indirect, subtle, or unintentional discrimination against members of a marginalized group such as a racial or ethnic minority."
At the core of its definition is "marginalization" which people in non-marginalized groups misinterpret all the time, especially when it comes to invisible disabilities.
Let's take Summer_Twilight's example:
Summer_Twilight wrote:
One time, I was invited to a black-tie event that I had been to before with an adult autism social skills group at an autism center. Being that I have an eidetic memory, I happened to remember a dress that the executive director was wearing the first time I went. During the third time, she let a close friend of hers borrow the dress. Being me, I tried to make a comment and remembered the executive director wearing it three years prior. She was embarrassed but was well aware that I am on the spectrum and thought I needed to be corrected. So she responded in kind by blurting out in front of her friends, "That's not appropriate, you can only say nice dress and that's it," before storming off to get the behavior specialist, who also attended the event involved. Yes, she humiliated me too.
The issue here is that an NT woman believes she is more marginalized than a disabled woman. Because she is not of a more marginalized group, it's not possible for her to experience microaggressions in this situation. In fact, you could argue that her behavior constituted a series of microaggressions towards you.