In most cases, you don't want to have customers write into your knowledge base. In those cases you need to make sure to review your tag permissions of the 'main tag' that appears to be your knowledge base.
Update permissions of the knowledge base
It's easy to manage these permissions. The first step is to go to the admin dashboard of your forum and go to '🔑 Permissions'. Then, click 'Restrict by Tag' and add the main
knowledge base tag(s).
A new permission row will appear, especially for the tag you have just selected. Make sure the '👁️ View discussions' is set to '🌐 (Everyone)'.
The '✏️ Start discussions' and '✔️ Start discussions without approval' options should be set to admins only (or eventually other knowledge base article writers/ranks). You can customize the permissions to what you need.
In the future this knowledge base software will make 'comments' available in knowledge base articles. It depends on the permission of the user if they're able to write comments.
Your permission list would probably look similar to this.

Knowledge base group
Do you have a great community, or you only want certain employees to have permission to edit the knowledge base, without full access to the forum? Then your best option would be to create a new permission group.
For example, create a permission group that's called 'Knowledge base editors'. This will be your employees who will write or edit knowledge base articles.

After creating your custom permission group, update your knowledge base tag permissions and add 'Knowledge base editors' to the 'Start discussion'.

End result
Eventually, your permission list may looks something like this:

Permissions can be complex. If you have any trouble deciding to who you grand permissions, let us know! We'll help you figure out.