Selected categories displayed out of order on main edit screen

[CircleReader]

(First time submitting a ticket...)

Fixed for Quick Edit in #19474, this is still happening in the main edit screen. Selected categories float to top upon updating the post, losing their visual relationship with other categories.

1. A selected child category, if the parent is not selected, is removed from its place under its parent and shown as a parent at the top of the list.
2. If both a child category & it's parent are selected, both float to the top, and the parent-child relationship is preserved visually.
3. In both cases, unselected categories remain orphaned at the bottom, with unselected child categories no longer shown as children.

[SergeyBiryukov]

This is intentional, see #10982.

A filter was introduced in #20054, allowing plugins to change that behaviour.

This plugin implements the change:
​http://wordpress.org/extend/plugins/category-checklist-tree/

[CircleReader]

Didn't find that one on my search. Thanks!
For the record, IMHO, the more categories you have, the more confusing this "feature" becomes.