The biggest complaint about Harper is that the quality of grammar checking still needs some work. I've got an exciting new project I'm preparing to discuss later this week (hopefully) in that area. It should be a step-function improvement over our previous methods for creating new rules.
In the meantime, I've collected some recent sightings of Harper in the wild:
This post was proofread by Harper.
I’m doing something very naughty on cam, don’t miss out. - https://telegra.ph/Enter-01-31?aleneab
I’m waiting for a real man to take control of me. - telegra.ph/Enter-01-31?Taupt
Back in my day, we used math for autocomplete.
It's not easy, but I think it's one of the best habits I've ever built.
It didn't work for me, and if you reading this, it probably won't work for you either.