LibreOffice only embeds fonts that have a license permission for that . That may create surprise in users when some fonts used in documents don't get embedded.
Our relevant help page  could include information about that.
For reference, some pages that MS has dedicated to this are , .
The Font tab of the Document Properties dialog should also inform user on the font licensing.
Olivier Hallot committed a patch related to this issue.
It has been pushed to "master":
tdf#141095 A note about font embeddable permissions