_Purpose: optimize Reverse-DNS operations_
1. Assumption: There is a ton of negative reverse-DNS replies (no PTR-record/NXDOMAIN) returned from the RIPE NCC rev-DNS-Servers, for all not-yet-delegated address-blocks they are responsible for (also called "lame" delegations?).
As others have pointed out, this is not a "lame" delegation. That would be a situation where authority for a zone is delegated to a set of name servers, but one or more of them are not configured to serve the zone in question. And, further, NXDOMAIN isn't really an "error", it's a code indicating that the queried-for name doesn't exist in the DNS.
2. Question: How could this be optimized or at least encouraged to be fixed?
Is this really an operational problem? If you think so, I think you need to explain in more detail why this is so, because it's far from obvious. As has been asked by others, doesn't proper "aggressive negative caching using DNSSEC" as per RFC 8198 take care of the "optimization"? And ... a member wanting to see these stats for address space they "own", they can just get the corresponding zones delegated and inspect this themselves... I'm with what others have said here: the proper venue for discussing this issue is the DNS WG. Regards, - Håvard