The backinflate faceplant is really a newbie use error. The first thing you need to be aware of is that a BC is only supposed to float your head above water and this only when you are conscious.
BCs are not Coast Guard approved floatation devices.
That said the problem is that people get used to the fact that most standard jacket style BC will get you higher out of the water if you overinflate. With a back inflator style jacket this is what causes the faceplant. So to avoid the faceplant simply do not inflate past the point were your head is out of the water unless you want to lean all the way onto your back.