The environment of the yoga class is particularly ripe for trauma triggering because of its inherently intimate nature, arising out of the integration of mind and body and the teacher's position as a leader and spiritual or physical authority, and the fact that trauma can be held in the body.
Yoga Teachers will sink or swim together. The sooner we figure out a sustainable win-win business model regarding how to freely share the benefits of this rich tradition, the sooner we will all prosper. Ommmmmmmmmmm.
The range of yoga practices is so wide that creating a single organization that certifies everybody who teaches yoga has not yet proven possible. So, for now at least, you've got to take matters into your own hands and check out different teachers for yourself until you find the one for you.
The way people approach life is the way people show up on their yoga mat. And yoga teachers are no exception. Some yoga teachers may lead with a sense of aggression and competition while others will promote a feeling of safety and peace.
At some point, every student must leave their teacher. It's a built-in principle of yoga. Parents raise children to be able to survive on their own at some point; its the same concept between teachers and students of yoga.
Yoga teachers, I would like to be taught by you, not "invited" to do this or that. "Make it feel good" is not an instruction. Neither is "do what feels right to you" or "this is the pose I suggest, but if you prefer another one, go ahead."