- Edited
Username fields on many websites have autocorrect enabled. This means that the first character of the username might be auto-capitalised.
If a site is using case-sensitive usernames, this can cause issues.
Example case - visiting https://orionfeedback.org and going through the login process.
Orion:
If you proceed without rejecting the correction, it will accept it and capitalise. Safari doesn't do this, and doesn't show the suggestion.
Safari: