As the person providing the quilt I would want to be consulted (in a straightforward, but not insulting manner).
As the longarmer I would expect to consult the customer before doing anything (or as soon as the difficulty is noticed, if partway through)
I don't think it is reasonable to expect a longarmer to catch/notice/fix any and all mistakes/oddball design moments - they are being engaged to quilt the thing, not evaluate/improve it. Some things are so bad that it can make the quilting impossible to do (e.g. monster wavy borders) others are easily quiltable (e.g. a reversed block) and may not be that noticeable (to anyone - the longarmer is human too). I haven't read the post that inspired this one, so don't know what the original issue was, but there are *many* different things that can come up - and they are all at various points on the 'noticeability' scale.
Of course there are always going to be people who will complain regardless of what you do. Anyone who has ever had a job dealing with the general public knows that!!
