Mrs B has a different Amazon account from me. But because her Macbook goes through the same Router to Virgin Media as my Mac Mini, our IP addresses are almost identical (the last digit is one different).
It seems that this is enough for Amazon to think we're review-scamming - she reviewed a book by her cousin, which she'd bought through her Amazon account (own name, password, etc), and asked me to review it too through my account. (a) They wouldn't let me! and (b) worse still, they deleted her review too!
Are Amazon likely to have see our fairly innocent reviewing as something more sinister?
Mrs B has just been poring through their Terms & Conditions, and there is an obscure rule about not submitting more than one review from the same household, so that's what we're guilty of!
//...our IP addresses are almost identical (the last digit is one different//
Those will be your LAN IP addresses, allocated by your router to your devices.
A website, eg Amazon, will be looking at your (single) WAN IP address, allocated by your ISP to the internet side of your router.