> Even with only about 1 in 1000 users enabling telemetry

How do you know the number/proportion of users who run without telemetry enabled, since by definition you're not collecting their data?

(Not imputing any malice, genuinely curious.)

Good question. We don't know the true figure, but we extrapolate the denominator from estimates of the total number of Go users and the fraction of Go users that run gopls.