I totally understand your point, Jollysure. But, I completely disagree with trying to change an animal's natural instincts just for convenience. Male Bettas are aggressive, solitary fish, for the sake of their own survival. Whether people were breeding them as fighters or not, they'd still be aggressive. It isnt a question of IF they'll kill or maim each other, it's WHEN. Breeding out their aggressiveness would change everything! Their spawning habbits would change, and they'd probably be extremely difficult to spawn. Would they flare as beautifully as they do now? Would finnage and quality be sacrificed for a peaceful fish? I'm totally happy with Bettas as they are, as they naturally should be.
This reminds me of how people try to alter breeds of dog that naturally have that instinct and have had it for 100's or 1000's of years. I meet a lot of people who meet my dog and ask about where they should go to get a Border Collie (or German Shepherd, or any other herding dog) with no-low herding drive. The answer is - NO WHERE. Good breeders would not breed to dilute the instinct of their animals, they breed to enhance and better them. Just like breeding Border Collies who will not herd is unnatural and irresponsible, so is breeding Bettas that won't flare or fight.
I also totally agree withSynirr, about the heavy finnage thing
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... Judges would definitely pick a proportionate, clean shorter-finned HM over a HM with extremely heavy finnage that weighs him down. It's not about length as much as it is about shape, proportion and health.