Shouldn't work should flag up an error saying this has already been added to another PayPal account. Same when you try and add the same card to another PayPal, gives you an error
One account per PP, never heard this happening before as the numbers would be an idential match? it would mean someone else could add that bank to their account and use that bank to "Fund" their PP and will get flagged. Did you remove it from another account?
keep us up to date please if it ever goes down hill for you... did you use exact same acct numbers/routing numbers on each PP or did you add like a random letter or number or something?