Dark theme affects content after code block

Summary

When a user switch to the Dark syntax highlighting theme, comments below a code segment look strange.

Steps to reproduce

1. Use Chrome or Firefox. This can’t be reproduced on Safari (probably because of WebKit).
2. Switch to the Dark theme.
3. Navigate to gitlab-org/gitter/webapp!1367

Example Project

See above.

What is the current bug behavior?

Comments below code segment look pale.

What is the expected correct behavior?

Comments below code segment should look the same as the one above.

Relevant logs and/or screenshots

Output of checks

This bug happens on GitLab.com

Possible fixes

I don't know.