Even when it's just one person who assumes that any original character of the same gender as the author MUST be a Sue -- of course!
I ran into that, stopped writing a story that I had been writing for a year or so, because it shook me to think I might be falling prey to such a stupid idea. Nevermind that the original character was quite ordinary, wasn't saving anybody or doing anything heroic or plot-forwarding, and was serving as the simple peasant stuck on the sidelines observing the heroes from afar. A bit like Merry and Pippin, except she never got to save Éowyn or Faramir.
All the other reviewers of the story chimed in saying she wasn't a Sue, but, well. Eight years ago I was less confident that I knew what I was doing than I am now.
I later realized the person calling my character a Sue was probably young enough to be one of my students, and didn't yet have the faculties or experience to observe nuances. She was thinking only in macros.