I'd apologize for it being a slow news day, but this was a pretty good rumour chain, so too bad. A few days ago, a SWTOR fan posted an email from BioWare's Customer Service team on Reddit's r/gaming community.
The email notes that the player was banned for "looting high level Loot
Contained on Illum (sic) while being well below the recommended level
for the planet."

On closer examination, many players
asserted that the email was fake (considering the spelling of the planet
Ilum as "Illum"), but that didn't stop the internets from spreading the
rumour that BioWare was banning players for visiting planets outside of
their level range. In fact, the gossiping had spread so far that BioWare's Stephen Reid decided to step up to the SWTOR forums to officially confirm that bans had taken place, but their motivations were entirely different.
According to Stephen, some players were traveling to Ilum with low
level characters in order to exploit certain core mechanics of the game
for large profits. To explain in some detail, it was possible for
players to use alternate characters of another faction to "flip" the
territory's controlling faction. Upon doing so, all resource nodes would
respawn, and some players were simply flip-flopping territory control
back and forth in order to repeatedly farm valuable credit lockboxes.

One player even went so far as to document the exploits,
noting that these particular players were using a level 14 Republic alt
in order to constantly shift territory control. Long story short, it
seems like these bans were in good judgement, and BioWare has certainly
set a strong precedent for any future exploitation punishments they'll
have to dole out.