It seems there is some other plugin/theme that also uses the coment_text hook and makes the restriction.
Please deactivate the plugins/theme one by one and check after each deactivation to find a problem maker.
Please check it here, wpDiscuz doesn't have any restrictions.
Besides wpDiscuz error messages are shown on the screenshot below. The error message you've shown doesn't come from the wpDiscuz plugin.
In case you want to say thank you! 🙂 We'd really appreciate if you leave a good review on the plugin page. This is the best way to say thank you to this project and the support team.
You should contact Yoast Comment Hacks support and ask them to remove the restriction.
In case you want to say thank you! 🙂 We'd really appreciate if you leave a good review on the plugin page. This is the best way to say thank you to this project and the support team.