Haha, Even Sourcing is an interesting thing. I never seen that particular name for it, I used to just think of it as Operation Log. My engine is written with a lot of that in place, many things are written as small virtual machines with very small instruction set. I do record some of that, but I haven't found it very useful with Google Analytics. Having complete traced in a somewhat managed way would be super nice, I might get to writing such a management system one day or find a good enough fit.
I work with git branches for features, seems to be fine. The project is so small that there's barely 2 people working on it, and I'm the only developer. So there's very little "process" in place.
Feature flags are an interesting concept too, I will give it more thought, right now I'm not sure it's a good fit for a few technical reasons specific to how the engine is implemented.
Thanks for the suggestions :)