Details block in Twenty Sixteen theme is missing the arrowhead symbol

[franzaurus]

Context and steps to reproduce

As reported on https://wordpress.com/forums/topic/details-block-missing-arrow-symbol/#post-4077606

In the page editor, an arrowhead shows you can click the details block to expand it. However, the arrow is absent when viewing the front page. This makes users aren't aware of the clickable section expansion.

Steps to reproduce:

1. Add a details block to a post or page on a website using the Twenty Sixteen theme.
2. Save and view the front-end.
3. Notice that the arrowhead is missing from the clickable detail block.

We expected to see the arrowhead in the clickable details block.

Site owner impact

Fewer than 20% of the total website/platform users

Severity

Moderate

What other impact(s) does this issue have?

No response

If a workaround is available, please outline it here.

This bug only impacted the Twenty Sixteen theme on the WP.com platform; other classic themes, such as Twenty Twenty, were unaffected. This bug is not present in the Twenty Sixteen theme used on self-hosted WordPress.org sites.

Platform

Self-hosted