Similar experience. Fix with inability to respond to some crazy github-generated email addresses rolled out publicly in less than 48 hours. It helps that I was able to tell them "I am pretty sure it's your regex on valid email addresses because I can reproduce it with other emails like $this"

I also recall they fixed an issue where "--" at the top of an email I was replying to was making the whole thing look like a signature and when I tried to send it was warning me about an empty message.