Will it harm the new plant if the seed portion of a sprouted avacado seed is removed ?

I don’t think you can remove the seed/pit without harming the plant (and why would you want to remove the pit?). Here’s how I’ve grown avocado plants in the past:
Take the avocado pit, wash it gently, then place three toothpicks around the sides so that you can prop up the pit over a glass of water so that half the pit is in the water and half is out. Put it in a dark place, like a cupboard or closet, and wait till it grows a long root and a little sprout on top. Remove from the dark place and put it in on a windowsill. Let the top sprout grow until it is about 7 inches long. Then, take a scissors and cut it down to half the size. This will make the plant grow out instead of up (I believe it is called the “apical dominance” of the plant). If you don’t snip the top off at 7 inches, it will grow really long and you will just have one long stem and leaves, rather than a big leafy plant, which is more appealing for a houseplant. At this point you can transplant into a pot with soil (still leaving the pit, roots, and stem/leaves) intact. I have only done this for houseplants, not sure if there are different steps to take if you want a tree that will eventually produce fruit, but it will take many years before an avocado sprout will turn into a fruit-bearing tree.

In addition to what @occ said – the pit is the part of the seed that the sprout uses for food. Removing the pit parts means that the young plant won’t be able to access most of the nutrition it needs to grow.