Wearing A Belt Is Fine
Not wearing a belt doesn’t necessarily mean an individual is going to pay closer attention in the Deadlift, any lift.
Dr Mel Siff stated that one of the advantage of wearing a Belt that it can provide feed back cues to ensure proper form.
Another benefit of wearing a Belt is that it increases back support. As per Dr Mel Siff (Source: Facts and Fallacies of Fitness) flexing the abs into the Belt increase back stability.
Back before Powerlifting Belt were around, lifting Belts were wide in the back and narrow in the front (Olmpic Lifting Belts, perse).
Powerlifter would turn the Olympic Lifting Belts around in front. This allowed a larger surface for the abdominal muscles to brace into, which increased greater back stability and support.
Low Rep Sets
High Repetition are contra-indicated for the Deadlift. That due to the fact that the lower back is quickly and easily overtrained, as per Dr Tom McLaughlin’s research.
You corrected your HIgh Recommendation down below but this post appeared to promote them.
High Bar Squat for Deadlifts
This is a good point. High Bar Quarter Squat, Front Squats, Leg Press, etc are great Deadlift Assistance Exercises; that since Leg Drive assist in breaking the weight off the floor.
To expand on that, in max or near max effort Powerliting Conventional Deadlift attempts, the back initiates the drive off the floor with some assistance from the legs (Research McLaughlin).
And how did you come up with these numbers?