At the Edit Post page you can find a commentary under the Excerpt field: "Exceptions are hand-crafted summaries of your content that can be used in your theme". A link follows, "Learn more about manual excerpts". The link points you to http://codex.wordpress.org/Excerpt, instead of http://en.support.wordpress.com/splitting-content/excerpts/. Both explanations are helpful, but this is wordpress.com. Thanks in advance for resolving this tiny mistake!
The blog I need help with is rechtsgeschiedenis.wordpress.com.