Originally Posted by R_Hythlodeus
It doesn't, but it advances the character. It is called character progression. We know Selvig from 2 movies now, in the last one he was taken over by Loki against his will. Now we learn of the outcome of this, just like Tony's PTSD, Selvig is not untouched by the events of TA. He had a god in his head and has to deal with it. You can't do that with Thor really, showing how big an event TA for the characters was, because out of all Avengers, the alien invasion wasn't a big game changer for him. For Selvig it was. Thor has to deal with his brother and what Loki did, but for Selvig it was a bit more. Being possesed by a god should be adressed.
I saw The Avengers
twice and I have no recollection of Selvig's involvement in that movie. I don't think it's a good idea to put aside the story of Thor 2 for several minutes to bring up a plot point involving a tertiary character from The Avengers
. Ideally Thor 2 should be focused on the story of Thor 2.
For this scene to work, you're expecting people to remember the fine details of a movie that came out over two years ago, and even then it's not a good idea as it builds up The Avengers movie and not Thor 2. Contrast this to TDKR when they talk about the effects of The Dent Act. It does build up TDK, but it is explicitly relevant to the plot of TDKR.