My American cousins would describe this selection to be "out of left-field" and rightly so. Steller is more of a story sharing app, and at it's best combines excellent photography paired with engaging narratives. Stellar's story building tools are template based, simple to use and make your content look slick very quickly. It has a similar feed scroll feel to Instagram, but clicking on a title page lets you delve into an in-depth project rather than just a collection of hashtags and comments.
The annual fee, however, is intended to help out the developing company, Vero Labs, by being its main source of income. The idea is for the platform to remain free of advertising in the long run and not to share any user information to make a profit. In addition, the company wants to generate revenue through transaction fees that merchants have to pay when selling products through Vero and implementing the 'buy now' button.
A simple chat (slack style) it's enough. Just having the possibility to send messages either single user or team (#channel). But please don't forgive to give an useful appeal to mobile app (worst error of competitors is, have a good app but totally no mobile friendly!) i would expect to have a similar whatsapp or slack app for messaging within the slack mobile app!