Does the MacBook Pro 15'' 8,2 Early 2011 accept both A1321 and A1382 batteries?
Regarding your statement that:


  But what about the early 2011 MacBook Pro 15" ? It seem that most vendors commercialize the A1382 battery for it, but some other commercialize the A1321.


I haven't come across this scenario, so can't comment on your source for this. 

However, officially the A1382 battery is compatible with all of the 15.4" A1286 models of MacBook Pro from the Early 2011 models up until the Mid-2012 models.

And, officially, the A1321 battery is compatible with all of the 15.4" A1286 models of MacBook Pro from the Mid 2009 models up until the Early 2010 models. They are not officially compatible with the Early 2011 models.

Were you to use an A1321 battery in the Early 2011 models you would be doing so at your own risk.