There is no bitcoin specification. Core, the reference implementation, is the closest we have to one. We've never had software that works like bitcoin before bitcoin.

> Core currently the reference implementation.

What is a "reference implementation"?

https://en.m.wikipedia.org/wiki/Reference_implementation

> [A] reference implementation [...] is a program that implements all requirements from a corresponding specification.

I'm afraid that the issue we have is not with the implementation, but rather with the _specification_ itself. It's about Bitcoin's _purpose_.

Core currently the reference implementation.

 consensus rules. Identical. The only way they differ (iiuc) is in mempool policy.

bitcoin

Other clients are a menace

ZezzebbulTheMysterious

Core currently the reference implementation. 

Knots is not.

Core and Knots share *identical* consensus rules. Identical. The only way they differ (iiuc) is in mempool policy. 