Ben May

This plugin prevents imposters from leaving comments on your website with either the same name or email address as a registered user on your site.
This prevents users on the blog from being impersonated.

Duplicate Comment Authors

Prevents people posting comments using the same name as a registered users display name.

Romulo Vieira

Restrict on which categories a user can post.
It also blocks the users from creating/editing/deleting categories.
Only Admins can set other user’s categories.
Works with Block Editor and Classic Editor.
It’s compatible with IE11.

Restrict Author Categories

Restrict on which categories a user can post. Just that!

Duplicate Comment Authors vs Restrict Author Categories