I've been looking at lots of photos on houzz.com to try to get some data as to where people put their knobs on shaker-style cabinets...and it seems to be a mixed bag with some putting them in the exact bottom or top corner of the door, and others purposely NOT on the corner.
Here are some examples of what I mean...
Centered in the corners:
NOT centered in the corners:
We originally preferred the NOT centered knobs, however, this is complicated by our super-high square cabinets that really can only have the knobs at the bottom of the cabinet, or they will be even LESS user-friendly... (still looking for step stool options...send them my way!)