For those who are unfamiliar with the concept of display burn ins, basically this is where an item on your display has been in the same spot for too long, resulting in that image being literally burnt into the display and leaving a permanent mark. This is also why screensavers were used in the past to prevent things like that from happening, but thankfully that will not be the case with the Galaxy S8.
This question was posted on Twitter to Samsung Netherlands in which they confirmed that the home button won’t be burnt into the display of your phone. The folks at Galaxyclub.nl have similarly tested this out themselves and discovered that the home button actually “shifts” or “jumps” around a few pixels at a time to prevent this from happening.
Note that this is also what usually happens in smartwatches with an always-on display, so it isn’t anything new, but just something to clear any doubts in case you had any.