If more than one player have the same character name, that name could be at risk of being lost. The way SWTOR prioritises it is as such: Subscribers have priority, then Preferred (ex-subs), and last Free-to-Play players. Then, they look at stats, the most times in game on that character, so the most played characters are safer than the least played characters, plus the higher level character is safer than a lower level character.

Read my full analysis of my characters plus what I plan on doing to keep the very same names in and of themselves.