I’ve been trying to reproduce this issue, but so far am not able to. With the default embed script, comments show up for me with no errors on both the latest Chrome and Firefox browsers (running on Ubuntu.)
One other thing to check is to make sure you’ve created the host record in the Admin / Customize / Embedding section of your site. I’m mentioning this because I was getting an error when testing this because I hadn’t filled in the “Username for topic creation” setting and saved the embedding settings.