I am productive when I am motivated and I have a good process in place. Now, the process is easier - it is a matter of forward planning and using the right tools. Motivation is hard, so I make sure I commit to things, for real. So that there is no way out. Even if you ave passion there can be tasks you don't want to do. So I keep myself accountable: for instance, making sure someone else relies on the work being done or betting money on completing the task.
It is very interesting what this app will become. It seems very likely that negativity will prevail unfortunately. Is the plan to introduce guidelines to tackle this? Is it enough to be pointed to a flaw to 'improve'? Perhaps, one needs to really trust the person who utters the criticism to accept it. I think the hardest thing about change is to persevere. To help with that the app could provide a framework for endorsing small changes towards one's goals.