Well, as you said, you can update your dialogue so the email address isn't asked until the point you determine them to be worthy of upserting in Marketo, or just use an SL filter (alternatively add those into to a static list as well) to find dynamic chat-sourced new people who interacted with the chat but didn’t reach the goal state, and then delete them. You can automate this process of removing people from the db as well using a simple campaign setup. Be mindful of the the fact that, delaying email address question would also mean that you won’t be able to update existing people in the db until you get their email address (at least for the non-cookied visitors), in case they don’t reach the desired goal state first. But, strategically, I don’t like the idea of not letting people stay in Marketo who came to your site and interacted with chat. Ideally, I’d rather use scoring/stages to differentiate people who reached the desired goal state vs those who didn’t.