My item has been soft-rejected and among the reasons listed were invalid markup. I’ve run the markup through the validator and there are a handful of errors, but they’re all in WordPress generated markup. Is this something I’m responsible for fixing? I would think the only markup I’d be required to validate was the markup I created.
WordPress do not generate errors. Can you share link or screenshot?
Google font error (if you are using) is ok. Themeforest review do not soft reject for that 
@sbp is right WordPress does not generate validation errors. If you have used WP default widget in more than one place, then you can get validation error of duplicate id. The other reason could be validation errors generated for blog posts. You can edit the blog posts to avoid those.
can you share the w3c validation link?
Thanks for the replies. Here are some examples of what I’m talking about:
https://validator.w3.org/nu/?doc=http%3A%2F%2Fdemos.themebright.com%2Fsteadfast%2F
1, 5 [Warning]: Jetpack Social Menu generated markup.
2–4 [Error]: WP oEmbed YouTube video.
6, 7 [Error]: Jetpack Site Logo generated markup.
https://validator.w3.org/nu/?doc=http%3A%2F%2Fdemos.themebright.com%2Fsteadfast%2Fevents%2F
1 [Error]: WP API link.
I’m a new user to the forums, so I can only post two links, but you can find these other WP errors at the following URLs (relative to home URL):
/blog/
1–2 [Warning & Error]: WordPress-generated attachment ID.
/2016/02/07/an-example-blog-post/
1–6 [Warning]: WordPress-generated comment markup.
/about-steadfast-fellowship/
1–3 [Error]: WordPress oEmbed video.
4–13 [Error]: Jetpack Tiled Gallery markup.
Disable jet pack plugin and retest it.
4 Year Old Topic