@Kamil_Czaja completely understand your concern about investing in a startup product, especially before a business model. We are lucky to be backed by some of the biggest investors and are in a very financially stable place. Our investors are confident in our business model due to the adoption we have already gotten at some of the biggest companies and have encouraged us to focus on making the product even better before having to worry about revenue. I’m biased but I personally have taken a bet on Coda having a bright future by coming to work here and can vouch for you to bet on it as well 
As for your other feedback, I completely agree that the ability to share only specific sections and lock down parts of your doc can be very useful and are both on our list of improvements.