I have my nature on my card set to adamant. And lo and behold when I caught Reshiram and Tornadus they both had an Adamant nature.
I have to do more research and catch more legendaries but for now I think it is purely luck.
I'm 99% sure it's all for show. If it did increase the rate of encountering a certain nature, I'd think I would of heard something across the multiple sources I check.
The Vermilion City Guru
Originally Posted by Neosquid
one of these days I'll manage to stop being an obnoxious fanboy...
Originally Posted by Mr. MR
Maybe I should do a couple of PotW