1. We track which GitHub usernames and repos that use Watermelon, it's the only thing we track. This allows us to go to people and ask them for more detailed feedback. We also get feedback from stargazers and forkers. Because we're open source, people also leave GH issues.
2. The incentive is something very basic: They wanna see a better version of this out there in the world.
Sorry, but I don't think you should request feedback from users without their explicit permission. Isn't there a feedback mechanism built into VSCode already, or make and affordance for one in your plugin UI? Maybe at best generate a random install ID that can be reset for analytics and session tracking? VSCode has guidelines for this, see [2].
[1] https://github.com/watermelontools/wm-extension/blob/c389125...
[2] https://code.visualstudio.com/api/extension-guides/telemetry...