I think that _page, _page_count and _total_items should not have the leading underscore as they are properties of the collection in the same way that a name property exists on a person.
I had a couple reasons for why I went with the leading underscore:
It’s metadata for the collection.
The collection resource can have data other than just the embedded collection items. I didn’t want to have conflicts with those (the likelihood of those having a leading underscore is pretty slim).
I’d be okay with removing the leading underscore, but those were my reasons for having them in the first place.
While I agree that it’s metadata for the collection, I would say that it’s primary data for the collection resource.
The conflict issue is something I hadn’t thought of, though I think a collection resource with an page and _page property would be very confusing in and of itself.
I wonder if there’s consensus in the wide API community on this?