Since Bob has no soul, there isn't any rubbing off on.
As to Bob's personality being so similar to the Harry version of Bob and the Butter's version, Jim explained that it didn't change that much since Butters first met Bob when Bob was still Harry's. First Impressions and all that.
Not true, Bob explains souls rubs off all the time, in warm feeling hugs. Harry describes Bob as his friend, Both of those are deductive premises to lead to a valid inference Bob has been largely effected by Harry. The name thing just gives it a structure to work around. Just like Belief in something is what gives it power vs the name that gives that power form. Then wizards aura's are described in miniature compared to say MW puts out, but is known to have some influence spill over, it's just considered Negligible usually. Years of close contact while Magic is actively worked around the same wizard and utilizing/tinkering with the wizards spells and enchantments him self as he does with both Harry(LC direct proof) and Bob(any SG reference) leads not only to direct contact with their magic but using it himself is a different form of magic than usual for spirits. That lead to a valid inference such things can have heavily influenced Bob.
Your first statement ignores all that seemingly? Of course we'll have to have a whole other thread for is magic, life, soul all essential the same positive energy in different levels of refinement, which I'm cool with stepping into that corner to swing it
But is otherwise showing valid arguments for a theorem towards influence if not soul itself.
The second part references what we know towards it, but what we know is as always incomplete. Had not Harry actually Met Bob under Justins tutelage? An if not, is he not simply collecting a mask of identity associated with the beliefs of those who have known him just like any diety gaining multiple formative mantles? He up till it's expulsion still had Necrobob But was not known as him. He's gained more than one identity based upon 2 separate groups of people and how they've known/interacted with him. Harry and Co, And Kemmler and Cowls group.
*That's a great way to describe it, he released the 'mantle' of evil Bob he'd had, his alternate identity to become it's own thing.
So still comes back to how similar the energies that make up the various forms of life are, But i'll reference my metaphor of the human body is a distillery of soul into life(which is where we have an issue in my theorum apparently) and life distills into Emotions and feelings which are fuel for magic, are magic itself(which is proven)