I just tried inspecting an element in Chrome and it didn't automatically expand to show the children. That's the behavior I would have expected. Interesting that it behaves differently for you. Are you sure you're not inspecting the child, thinking you are inspecting the parent, which would appear to be expanded in that case?
Firefox offers a dark theme in the inspector's settings, maybe try that. I personally don't like it though.
Hrm. Maybe the difference I'm noticing is that if I click on text, Chrome will expand the surrounding tag (e.g. <p> or <a>) while FF will keep it closed.
I haven't done any side-by-side testing of Chrome and FF (and am currently not working), so I can't reproduce the issue now.
Firefox offers a dark theme in the inspector's settings, maybe try that. I personally don't like it though.