Keybase/Steller incentivised spam has also apparently been the inducement for much of the vacuous-but-annoying "great post" and "hello" comments infesting HN in recent months (per exchange with admins).
So yes, it's had an effect here as well.
So yes, it's had an effect here as well.
They should have just given coins to existing active keybase users. They would have had healthy increase in users based on regret and fear of missing out again.