Most dialogs in LibreOffice (but not the main document windows) have a pattern drawn over the title bar, which obscures the window title. I can't find any way to change this: changing the symbol style has no effect, and I can't find anything about this problem by googling.
I attach a screenshot of the Format dialog from Calc to show the problem.
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: libreoffice 1:5.1.4-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-38.57-generic 4.4.19
Uname: Linux 4.4.0-38-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: GNOME
Date: Tue Oct 18 13:38:16 2016
InstallationDate: Installed on 2014-11-26 (692 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
SourcePackage: libreoffice
UpgradeStatus: Upgraded to xenial on 2016-07-25 (84 days ago)
I installed LibreOffice 5.2 from the libreoffice/ppa PPA, and that seems to fix the bug. However, I obviously can't tell whether the bug is fixed in Ubuntu proper, unless the packages from the PPA are adopted precisely as-is!