[css-lists] Are outside markers out-of-flow?

The spec used to explain outside markers using position: marker, which counted as absolutely positioned, and thus out-of-flow.

Then position: marker was removed, and in #3771 @MatsPalmgren claims that abspos may not be web compatible. But maybe we can agree on whether they are out-of-flow or not?

This matters for example when propagating text decorations:

the decorations are propagated to all in-flow children

Consider this testcase:

<a href="">
  <div>item</div>
  <div>item</div>
  <div>item</div>
</a>

div { display: list-item; margin-left: 40px; white-space: pre }
div:nth-child(1) { list-style-type: decimal }
div:nth-child(2) { list-style-type: "1. " }
div:nth-child(3)::marker { content: "1. " }

Firefox	Chromium LayoutNG	Chromium legacy

Should the markers be underlined or not? I think taking them out-of-flow (and thus not underlining them) looks better. I guess they could then be painted at step 5 with "non-positioned floating descendants" https://drafts.csswg.org/css2/zindex.html#painting-order

Read the issue discussion, the linked CSS Text Decoration and CSS2 painting-order sections, and the referenced #3771 discussion. Use the provided testcase to compare marker behavior across the cited implementations; done means the working group resolves whether outside markers are in-flow and updates the relevant specification text.