Thanks for the replies, all. This was a somewhat hypothetical
situation, although I do occasionally run into it! It's not uncommon
at work to glue up panels prior to face-jointing the boards, for
expediency, and then surface them after, as someone mentioned. If the
boards aren't hammered into close enough alignment in the rack, we
occasionally get an uneven glue joint even after taking them to final
thickness. If it's a full 16th, and it's not going to be sandblasted,
wire brushed or chalked up to "rustic" (we use reclaimed timber almost
exclusively) then we toss it. But usually they're much lighter than a
16th and we can just feather it in if needed. I have used a block
plane to do it in the past.
JP