Both this and problems like LukeShu mentioned. For example, I had a problem where org-mode would hang in certain cases when using \mdash with pretty-entites tu

Both this and problems like LukeShu mentioned. For example, I had a problem where org-mode would hang in certain cases when using \mdash with pretty-entites turned on. Or csharp-mode would hang when editing around preprocessor directives. Emacs becomes non-responsive in such cases. It would be cool if I could just close that buffer, like a browser tab that had crashed. This and the fact that all async processing has to be done through OS jobs (or something like that) make it unsuitable as a replacement for many kinds of app.