“Bare feet or flat shoes for deadlifts?” - Chris White
How thick are the soles on the flat shoes?
For deads, it is not only acceptable to pull in socks or bare feet; it is encouraged. The closer your feet get to the ground, the shorter the range of motion your deadlift becomes. To understand this concept, imagine you’re deadlifting while standing on a 4" block. The bar will have to travel an additional 4" to lockout. The same is true if you wear Nike Frees or old school Converse Chuck Taylors. You will have to pull the bar through a greater range of motion.
Pulling without footwear has another benefit too. You are more stable. If you deadlift with a shoe that has a spongy sole, then your feet will be shifting around when you lift the weight. The goal when deadlifting is to “anchor” yourself into the floor, setup in a good position, and create lots of tension before the bar even moves. This can’t happen if you are wearing the typical running or training shoe that most lifters wear.
If you like the feel of a shoe, your best bet is a pair of flat wrestling shoes.