This topic keeps coming up.
If you hold the feather in the clamp from the jig and run the quill along on some 120 grit sandpaper you can take off some of the excess and the feather will sit much straigher. Basically fletchings are poorly prepared, but then they are relatively cheap. I actually touch mine onto the belt sander running an 80 grit belt, but it takes some care.
Note, this process can actually help 'em lie at the right angle as in the raw state they often don't sit up vertical from the shaft, more like this / than | . By holding the clap at the correct angle you can get 'em to sit much better.
For flight arrow fletchings I take 'em down so that there is barely any quill left, it also solves the problem of the quill scratching your hand.
Like most things, the finish is proportional to the time and effort applied... the devil is in the detail.
Del