Currently, the default value for rule-visibility-items is set to all. This means that rules will by default be shown even in segments where there are no items around the rule or when there is an item only on one side of the rule. This works as intended for grid, so no need to change it.

However, in the recent F2F an example was brought up for multicol https://www.software.hixie.ch/utilities/js/live-dom-viewer/?saved=14470, where all would create backwards compatibility issues since currently column-rules in multicol essentially behave as rule-visibility-items: between where they are only painted when surrounded by content on both sides. Details on rule-visibility-items can be found at https://drafts.csswg.org/css-gaps-1/#visibility-rules.

As a result, we'd like to propose auto for this property (and make it the default), so that we can resolve to all for grid containers (which is the current default) and to between for multicol containers to address backwards compat issues.