I would first be worried that you felt the need to create a data- attribute called "form" for a bloody form tag. Seems a bit redundant.
I would then be worried that you felt the need to create a data- attribute called "form" for a bloody form tag. Seems a bit redundant.
I realize this is in fact only one thing, but it is such a colossal sticking point I felt it warranted being repeated.
"c-form" is also painfully vague... We already know it's a form, hence it being a form TAG, WHAT is it a form OF?!?
For ME, I can't use attribute selectors yet, I'm still supporting too many users at places like healthcare and government offices who are on browsers that don't support them yet -- so it's not even a choice anyways.
Though since you said you're using BEM, that probably means endless pointless classes for everything and failing to leverage selectors properly; at which point why are you worried about one more class?
In all likelihood that alone probably means the whole codebase needs a good toss in the bin and a complete restart from scratch.