+1. Snapping candidates is a brilliant concept! But as OP mentioned, it is easy to bestow candidate status accidentally, and then impossible to revoke it (without designating a number of other candidates).
Also: highlighting the first letter in a snap candidate text box is awkward. Can we not highlight the bounding box instead?
Also: would love snapping for distance distribution, as Adobe has done for all their core design apps. (I'm not a Publisher user, so I'm not sure if it's there already.) For example, if I have three identical objects in a row, all 20px apart, and I create a 4th one, I would like it to snap to the same 20px mark.