That pretty much says it...God, this reporting Bugzilla thing is a pain! It's worse than working in Wikipedia!
On pc Debian x86-64 with master sources updated yesterday, I could reproduce this.
I don't know if it's a bug, an enhancement or the fact that "Insert" doesn't appear is on purpose.
Anyway, here's a code pointer:
webistrator: if you want Bugzilla improves, you could detail the problem. Since we try to have 1 problem/1 bugtracker, I suggest you to create a new bugtracker, I think it might be easier now since it won't be the first one ;-)
Bimodal for Insert/Overwrite is by design, changed May 2012 with http://cgit.freedesktop.org/libreoffice/core/commit/?id=b30e202861e9bdba4d86e76ba8a6f059da8efc31
Have open UX-Advise issue on what to do with UI for the the Insert-Overwrite/Caps lock/Number lock mode on the status bar as bug 88296.
*** This bug has been marked as a duplicate of bug 88296 ***