Spacer

Where it is right

Markdown. An author writing a post has no markup to hang a margin on. The alternatives are an empty paragraph, a <br>, or a ---, and --- is a semantic thematic break that merely looks like a line - using it for spacing puts a section boundary in the document outline that the author did not mean.

Given that something is going to be written there anyway, it may as well take a step on the scale rather than a number somebody picked, and it may as well be able to draw the rule a writer was reaching for.

That gap is a spacer with a label. The rule sits in the middle of the space rather than at its edge, so what is above and below stays symmetric and the spacer keeps the height it declared.

In Markdown

<!-- ::start:spacer size="6" label="Later" -->
<!-- ::end:spacer -->

<!-- ::start:spacer size="5" rule="true" -->
<!-- ::end:spacer -->

size is a step from 1 to 7. A value outside that falls back rather than throwing, because a bad attribute in a document should not take the page down.

Accessibility

A spacer with no label is aria-hidden. A gap is not content, and announcing one is noise in a screen reader for something a sighted reader experiences as nothing.

A spacer with a label is not hidden, because at that point it is a caption.