After playing for a little over two weeks, one Reddit user decided to return to the system he started the game from. After many hours of travel, he finally made it back to where his journey had begun only to discover that all of the planet locations, plants, and animals he named were reset. He traveled to some of the neighboring star systems and found that all of the names he created were wiped, too. His planet and star system names were still intact, but everything else was wiped from existence.
 

Update (08/27/2016): The user who first discovered that No Man’s Sky wipes your discoveries has updated his post to reveal that after re-downloading and reloading the game several times, his discoveries reappeared. The user believes it might be a server bug that is causing this issue. You can read more in the updated post.