Could an ankle fracture be practically painless?

There should be pain: Fractures are broken bones, and there will be pain when a bone breaks. Different people have differing perceptions of pain, so it's possible for somebody with a very high pain tolerance to say his ankle fracture was "practically" painless.

It can: Sometimes the fracture is of one bone only or may be small enough that patients will present with complaints of long term pain they thought was a an ankle sprain.

Yes: Some people have a minor ankle fracture. Others have a high tolerance to pain. Others have neuropathy and cannot feel pain normally. But, most people will have pain when they have an ankle fracture.