Created attachment 78340 [details]
Luna Element 5.1 Blue and LO Writer on a 1024x600 screen.
When some custom visual styles are used (for example, Luna Element or Royale Vista), LibreOffice's menus and toolbars may become much taller than necessary, taking lots of screen space.
This doesn't happen with other Windows software, so, I guess, the bug is located in LO's UI.
Note: installing custom themes may require patching uxtheme.dll, which violates MS' EULA. To avoid this, one can use software such as Styler (which allows to use custom styles w/o patching the library).
*** This bug has been marked as a duplicate of bug 30891 ***