I hit this every time I accidentally leave an unescaped and unmatched bracket in a Regular Expression search, e.g.
when what I meant to search for was
Instead of reporting it immediately as an invalid regex (as for example Notepad++ or Oracle regexp_ functions would do), it hangs for ages. This still happens in 14.0.6.
And if you are revisiting REs, it would be super handy if we didn't have to escape the space character (again, similarly to Notepad++ and Oracle regexp_ functions).