ADFs carry no pathogens almost ever that can infect a betta. Yes their bioload is a wee high but anyone wanting too keep aquatic animals healthy should have a filter and cycled their tank so this too should be a non issue.
Not good enough odds for me to risk it. People get lazy..they don't test the water. They do not change it enough, or start to slack. Not all, but many.
(betas) don't need friends. Thats a myth
I think it's a myth that it's a myth.
ALL living things gain from outside stimulation. Bettas live near other bettas in the wild, and do interact. They hunt their food, defend their territory. Come together to mate. Even solitary animals have some
stimulation from life wherever they live.
To me there is nothing more sad than a single betta just sitting on the bottom of his tank with nothing to do except eat and what happens after.