So I'm not sure if this is just 4.8.1 or if it would have occurred earlier, but we just tried to move a page using the Page manager under the admin tab and it did two things:

1) Renamed all the tabs with a "..." for each level below the root (so several are now named ...SomePage or ......AnotherPage).  This is bad. (I ran a SQL script to fix it though)

2) When a page was moved, it moved all sorts of pages under it as it's children where they were not previously the children.  We didn't click "move right" or "move left", we clicked "move up".  So uh, why did it decide to move all sorts of pages under it?

Now here's the kicker -- I can't duplicate this on a smaller site (ie 20 pages), but on our intranet site (600+ pages) it happened.

I don't know if I should report this as a bug or not because it is very difficult to reproduce and may be related to our specific portal and setup.  We're going to see if we can reproduce over and over again (made backup of database so I can rollback if we really foul it up).

Ok... this has been a while but I now can replicate this bug.  Open a page that has children (open the settings for it) and then check "Copy Design to Children".  This will then rename them all with the "..." prefix for each level deep it is.  This doesn't affect the hierarchy (as I previously thought). 

When I get a moment I'll post this to the bug system.