CSS counters break, at least do not increment, when using "display: contents" on the elements ancestor within the "counter-reset" container. testcase -> http://jsfiddle.net/5rcjk9gv/3/ Test case is straightforward, the first box does not use display: contents, the second box uses it on ancestors of the items that want access to the incremented counter value, but it's broken :( This isn't broken in chrome or firefox.
Sorry testcase url is -> http://jsfiddle.net/5rcjk9gv/4/
Pertinent (open) issue in csswg drafts relating to display box generation and counter interactions, though not exactly about the bug here in safari... https://github.com/w3c/csswg-drafts/issues/674
Confirmed this is still an issue with Safari as of 13.0.4. Does not match either Chrome or Firefox's behavior.