Yes the karma/applaud is the same as thanks.
You haven't really missed out at all, it just means your ready to start flashing ROM's, rooting is easy enough on the GS2 so you bypassed an easy step. Just join XDA Developers and do some reading, I'll help where I can but I'm still learning myself even with previous Android experience!
EDIT- I can't believe somebody would sell a device with accounts still attached, I wiped my X10i with the intention of selling it but I just can't do it and I'm still getting my flash fixes with it too! lol
There are 3 ways to reset the GS2, the option in settings then the recovery reset and a dialler reset but I can't remember the dialler number of hand. I will add though that if you remove the previous owners account details any paid apps will be lost and also if you restore a nandroid back up the previous users account will be back so that kinda devalues that idea.
Another option would be to install Titanium Back up from the market and back up all the apps you want to keep, you can then restore those once you factory reset the phone although I don't think you'll be able to market link any paid apps. Try it, you never know until you try!
Swyped from a distant star, the other side of the Galaxy on my GT-I9100 using Tapatalk ©