Firefox's Tracking Protection feature blocks some cross-site comment services. That is because they can track your browsing among different sites that use the same service. As a test to see whether this is the problem on Yahoo, you can turn off protection for the site. Here's how:

Click 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.

Firefox should reload the page automatically, but if that doesn't happen, click the Reload button on the toolbar, or press Ctrl+R.

Any difference?

Tried it after loading different pages. Same result. Works fine on Chrome.

Could you test in Firefox's Troubleshoot Mode? In that mode, Firefox temporarily deactivates extensions, hardware acceleration, any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem.

If Firefox is running:

You can restart Firefox in Troubleshoot Mode using either:

• "3-bar" menu button > Help > Troubleshoot Mode...
• (menu bar) Help menu > Troubleshoot Mode...

and OK the restart. A small dialog should appear. Click the Open button.

If Firefox is not running:

Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.) A small dialog should appear. Click the Open button.

Note: Don't use the Refresh without first reviewing this article to understand what will be deleted: Refresh Firefox - reset add-ons and settings.

Any improvement?

Ref. Use Troubleshoot Mode in Firefox

Went through your suggestion. Did troubleshoot mode but did not do a refresh....same problem.

FYI---- Just fired up an old computer. No problem!!!...??

Yahoo's servers tend to get overloaded by traffic.