I discovered this too. No items at light/dark side vendor and also all str loot from Black Talon was heavy. Time to respec:( I'm only lvl 12 but it's still few hours down the drain).
I add my vote to this thread. The GTM has very bad usability. I'd like to change it soon. Vendors also have similar problem. It's impossible to filter out only the gear I can use and buy (ex. show medium armor only or show only pistols).