Landing in LibreOffice Git last night was the change enabling the new layout engine by default. The new layout engine landed in Git a few weeks ago but was disabled by default while now with fixing early fall-out the developers have decided to turn it on by default. The commit explained, "The handful of bugs reported so far have been fixed, and I think it had enough basic testing to show that it is usable and can be switched on for wider testing. We can always revert back to the old engine if needed before or even during 5.3 series." The new engine can be disabled at run-time via the SAL_NO_COMMON_LAYOUT environment variable.
This new layout engine is known as the CommonSALLayout / Unified Text Layout engine. This work started out as a Google Summer of Code project. This new layout engine strives for similar glyph rendering across all platforms, HarfBuzz is now used on all platforms, the new layout engine integrates with the Windows rendering stack, the MacOS code uses the CoreText API, and on Linux systems Cairo continues to be used for drawing. More details on this layout engine work for LibreOffice via this GSoC student blog.
Enabling this new text layout engine by default is just the latest of many features for LibreOffice 5.3. The LibreOffice 5.3 open-source office suite is due to be released in late January or early February.