Jetpack Related Posts Not Showing When Published

Could you try to deactivate the WP Super Cache plugin, and let me know if it helps?

It seems to be outputting the following code at the end of the page generating the Related Posts:
<!-- Page not cached by WP Super Cache. No closing HTML tag. Check your theme. -->

If that solves the issue, I’d suggest checking your theme as mentioned in the WP Super Cache message.

Let me know how it goes.

I’m afraid the error message is still there right now, breaking the Related Posts call:
http://klassykinks.com/travel/how-i-travel-so-much-on-a-graduate-students-budget/?relatedposts=1

Could you try to fix that error by following the instructions here:
https://wordpress.org/support/topic/plugin-wp-super-cache-error-no-closing-html-tag-not-caching?replies=5&view=all#post-1506791

Another way to check for plugins using an output buffer is to deactivate all other plugins, one at a time, until the error disappears.

Let me know how it goes.