AQ salt is better then a lot of medications when treating certain ailments, but over use, long term use it is dangerous and harmful to the kidneys/liver. Bacteria and fish also become resistant to the salt in time when over exposed.
10 days is the typical treatment period, but up to 14 is safe- if more time is needed in treatment it is ideal to remove the betta from the salt for 5-7 days before starting back up on salt, to give their system time to clear itself.
Salt is good at cleaning wounds, ridding of ich, and killing off bacteria- but only when used properly.
I admit I didn't read the full article, I skimmed through it because I've done a lot of research in the use of salt, and follow guides set up by vets and very experienced betta owners. But I'm glad you found it and shared, as there are a lot of misunderstanding of the use of salt and it's affect on our fishy friends.
@BettaBlaze- high protein diet, regular weekly water changes and Stress Coat will help the growth of fins.