Earlier today the Guardian reported on mounting "fury" over a mysterious "Error 53" appearing on iPhones repaired by unauthorised repair providers. The report includes a quote from an unnamed "specialist" journalist (whatever the hell that is) who claimed that Error 53 will "will kill your iPhone". But let's roll that back a little, because Error 53 isn't doing the bricking. It's a symptom of the bricking, and that bricking is actually a security feature working as intended by Apple.
The Touch ID sensor is uniquely tied to the iOS device so that a thief couldn't do something like snag your phone, replace the sensor and then have access to all the credit cards you've linked to Apple Pay.
iOS device repair companies like iCracked are well aware of this feature and will actually manually move the Touch ID sensor from the broken glass face plate to the new face plate to make sure the phone stays functional.
Apple confirmed to Gizmodo that this is a feature and not a mystery error punishing you for using an unauthorised repair provider.
We take customer security very seriously and Error 53 is the result of security checks designed to protect our customers. iOS checks that the Touch ID sensor in your iPhone or iPad correctly matches your device's other components. If iOS finds a mismatch, the check fails and Touch ID, including for Apple Pay use, is disabled. This security measure is necessary to protect your device and prevent a fraudulent Touch ID sensor from being used. If a customer encounters Error 53, we encourage them to contact Apple Support.
The best bet to keep your own iPhone safe? Make sure the guy fixing it actually knows what the hell they're doing.