The one thing I know about keeping bettas in a community tank is that they like to nip at other fish with long/colorful fins or if the other fish have feelers.
-Josh
On the other hand you don't want someone nipping at your bettas fins either. I take all the fin nippers back to the store because I hate seeing them snap at his tail ,only happened 3 times, a neon tetra, a platy and couple of glass fish (barbs or something,they WEREN'T the dyed kind of glass fish)
Mines in a tank with a couple of clown loaches,2 balas,some guppies & platties,a few glow light tetras and a pleco
Everyone gets along at this point,really the only troublemaker is my betta,he's such a little bully and he rules the tank