There is a Galactic Trade Market area on your faction's home planet (you get there after you "finish" your starting planet missions) and also there are Galactic Trade Network kiosks on your factions fleet once you get there at around level 10 ( just click on your map on fleet and you will see a section that says Galactic Trade Market (its in the bottom left of fleet map on the Imperial side)
If you have multiple characters and don't feel like doing all the same old side missions, I like to do it like this:
do GSF class missions/side misssions until level 10, At level 10 you can incorporate Warzones to start leveling, Then at level 15 just do Class missions and Kuat Drive flashpoint (with all XP buffs) for fast leveling....but only good if you are tired of the repetitive side missions on every planet.
It does it for me too on my bounty hunter (I thought the lisp was hilarious) but only when I do the cartel bazaar bounty mission. Any other missions and its no lisp.
This probably happens be cause you are seeing people who leveled up following the story line, and fresh 50's who are shocked at how easily they are killed