Many sites rely on comment systems maintained by other companies. Because those comment systems are embedded on many sites, their cookies can be used for cross-site tracking. As a result, they sometimes end up on the Tracking Protection block list.

To test whether this is the problem on Yahoo, you can turn off Tracking Protection on Yahoo. Try clicking the shield icon at the left end of the address bar (next to the lock). On the drop-down, click the blue slider switch to disable protection.

Any difference?

If I use Chrome I have no problems. I can see comments and after I sign in I can make comments. Yahoo accepts my replys. I have been using firefox for years but only in the last year or so become a problem. some update added has been poorly thought out. I prefer fire fox's lay-out over chrome but I am being force to use chrome to read and participate in reading articles on yahoo.

Maybe Chrome doesn't have Tracking Protection, or its list doesn't include comment systems...