Sometimes it happens that you answer your own email to complement it with some information or follow up on the discussion. When that happens, aerc puts yourself in the "To:" field since you're answering your own email.
I think your own email should be ommited from "To:" when replying to yourself, unless it's the only one.
Can you test that out and see if that works for you?
Just tested it and works great!
I tried replying there on the thread but my message fell out of it. I don't have the time to investigate that further today, but I'll try another day.