I want to know if I should remove the leaves on my potato plant as I bury it more after it has grown 12" or so. Or do I leave the leaves on the plant?
There are a number of reasons for hilling (it isn't 12" btw) is"
Protect the tubers that are usually at the top of the soil from sunlight that will make chloroplasts 'wake' up and turn your potatoes green. That is a toxic potato.
To grow more potatoes vertically, closer together, take advantage of pots and better soil, get bigger and more potatoes.
The basics are to dump soil around your plant and leave at least 6" of top growth. When the top growth gets taller you do it again leaving a good 6" of photosynthetic top growth. Don't worry about trimming leaves off your potato. This plant is very different than most other plants. This hilling is only applicable to potatoes and...peanuts? A few others I am not remembering at the moment but didn't want you to try this with just any old plant.
You can also do this in a big pot of potting soil. Soil in potting soil is usually a bit on the acid side and potatoes love acidic soil almost as much as blueberries.
Another reason is that once you've grown any of the Solanaceae family in the soil you use today you will not be planting any of those plants of this genus in that soil for at least 2 years. That includes tomatoes, eggplant and peppers as well as all potatoes. Using pots is a great way to enlarge your garden and manage disease!
This is called 'rotation' of crops and is true for other groups of families such as Cur-cubits (melons, gourds, cucumbers) and Brassicas (Broccoli, cauliflower, kale).
Plant your certified seed potato in the potting soil, in the pot. Install a large tomato cage. As your potato grows, when it gets 8 inches high, fill with 2" of straw. When it grows a few inches higher pack in more straw keeping 6" high of top growth. This is essentially hilling using straw instead of soil. You need to keep an eye out for tubers getting sunlight and pack in more straw. I've also taken a black plastic contractor's bag to drape on the outside of that wire cage, like a skirt.
Don't worry about the potato leaves you cover up.