Can't post comments in Firefox

People are unable to post comments on my blog when using Firefox. My blog is using the Twenty Eleven theme and no additional comments Plugin.

There appear to be two similar results when people try to comment. The first result is, they can type in all the boxes, but can’t see what they’re typing. If they hit submit, their comment will go through. The second result is, they can’t see what they’re typing, and the comment will NOT go through.

Comments in Chrome work just fine.

Here’s the link to my site, in case this helps any: https://hikeswithdogs.com/

How can I fix this issue?