YouTube disables the comment button by default, and only enables it once text has been entered:
The general consensus on ux.stackexchange.com is to not disable submit buttons and wait to present errors until after the user has hit the submit button.
- Form validation and disabled buttons
- Disabled submit button on form vs allow submit then show errors?
- Disabling submit-button until the user has completed the form
Would this mean that YouTube is going against best UX practices? Or is this justifiable behavior?