Dropped a folder with a small HTML project, and after 20 seconds got "Something went wrong. An unexpected error occurred. Please try again or contact support.".

Note how the error has zero information.

Looking in the network tab, a POST request to /upload returned 403 and an HTML page starting with "Sorry, you have been blocked", and to "email the site owner to let them know you were blocked".

I'm very tired of this adversarial approach to software coupled with vague errors.

EDIT: it was the file './git/hooks/fsmonitor-watchman.sample' created by default on git init. Maybe because it's Perl. Worse-than-useless "please try again" and "you've been blocked" for committing the sin of uploading a folder that's a git repository. Sigh...