flaring isn't always a sign of aggression. bettas use it as a general mode of communication, it means they want you to notice that they're there (hence why males will do it to females before breeding) i've always taken it as a sign of health, though, since more animals will try to hide and be as unnoticable as possible when they're sick.
So remember, when you're feeling very small and insecure,
How amazingly unlikely is your birth,
And pray that there's intelligent life somewhere up in space,
'Cause there's bugger-all down here on Earth.
Loki/Grendel/Gail/Beowulf/Camilla/River/Bathory/Arwen/Lafayette/Deb/Jack Skellington (soon)