I believe it was intended to help prevent the edge of your finger from getting pinched under the tip of the trigger as you pull it. Honestly, I've never found pinching to be an issue but, the irritation from the groove certainly is.
You can certainly sand it down to eliminate the groove.
I definitely recommend the mod. I've found it to be a nice improvement that fixes the problem. Sorry I don't have a better picture but, hopefully this gives an idea on how much less interference there is. On this one the sanding is rough. I'd probably recommend working down to a fine grit and polishing that area to remove any remaining discomfort after removing the hump.
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