If a library allows anonymous suggestions it looks like those are showing to all patrons. Since the anonymous suggestions do have a borrowernumber I'm not sure how or why this is happening, but I have seen it with my own eyes.
There is certainly some weirdness going on here, I have tried a few things now and there is something seriously wrong:
1) If Anonsuggestions is activated, I don't have a 'my purchase suggestions' tab in the patron account.
2) I had created a few suggestions from my account (logged in) and then set the AnonymousPatron to 'not my borrowernumber'. Suddenly my own suggestions are no longer accessible at all, not via the patron account and I am also not seeing them in the purchase suggestions list.
*** This bug has been marked as a duplicate of bug 4137 ***