Here is the blog:

www.robjess.com

I recently upgraded to 4.23 and my comments stopped working. I have enabled them in the control panel. But when you click on the Comment Link it takes you to the entry but doesnt allow you to enter a new comment. I then deleted my MT install and reinstalled from fresh hoping that this would fix the problem, but it still isnt working. Does anyone have any ideas on what the problem may be or how I may fix it?

Thanks in advance.

Did you rebuild after enabling comments?

Yep

Can you check that your preferred archive type entry (Preferences>Publishing) this controls the permalinks used when commenting. If your preferred archive type is monthly or category then any permalinks will only go to the index page for that type.

Through the power of Google I got to a page that I could comment on but got a 403 permissions error You don't have permission to access /mt/mt-comments.cgi on this server when signing in.

Thats it! It was because publishing was set to Monthly. Changing this to individual now allows comments. Thanks