When I was at AWS, our team used to (religiously / proactively) keep track of customers having multiple complaints, especially repeat complaints (all of which manifested in to some form of downtime for them). Regardless of their spend, these customers ended up getting the "white glove" treatment, which otherwise is reserved for (potential) top spenders (though, engs are mostly oblivious to the numbers).

This is besides the fact that some account managers & support engs may indeed escalate (quite easily at that) to push product eng teams to really & immediately pay that tech debt that's hurting their customers.