The way I think about it is; second person speaks to the user, and first person speaks for the user.

Your invite modal is a great example of doing both in the same screen.

I avoid personal pronouns if I can, and default to second person when I can’t. This keeps the option open for both the interface and the user to use first person to refer to themselves.

Even better to have a good UX writer on the team who thinks about stuff like this :). Great article!