When some hair is shaved in an undercut, when yo go for a reshave, will the barber slightly cut abit more hair from the line each time? So over time, you end up with a severe undercut.
Not if you have a good barber. The one I have now has not cut one
extra hair yet. Its easy to check. Watch while thay are cutting and
see if any long hairs come off. Also if your hair is tied back, when
they are done take off the tie and comb your hair. If any cut hair
comes off in your comb, then its time to talk to or change your
barber! Once you have an undercut when you go for maintainance cuts
the barber should be cutting off only hair that's about 1/2" or so.
InUtero, you worry too much, man!