Should references to the appendix be removed from a camera ready paper? It is not uncommon for conferences in say theoretical computer science to have a strict page limit for the camera ready version (like 12 pages). In addition, the original submitted papers might often contain perhaps even a long appendix.

The submitted paper might postpone proofs to the appendix, or say something like "due to lack of space, you can find this and that in the appendix". However, for the proceedings, it is my understanding that the appendix is completely omitted. I think I have often seen proceedings papers which make "forward references" to the appendix, but strictly speaking this makes little sense because there is no appendix. 

So should one remove all references to the appendix in the camera ready version? Or do people typically not care, because it is understood that there is an arXiv version, or because a full version will appear later, or something else?
As a general rule, papers should be self-contained. A reference to an appendix would violate this rule if the paper is distributed without the appendix.

Instead, a best practice is to have a reference to an extended version of the paper that includes the appendix:


  The proof of this result is provided in [1].
  
  
  A. Nonymous: How to write a paper (extended version). 2018. Available online at http://arxiv.org/some/url
  


The extended version would then have the same sentence, but with a reference to the appendix:


  The proof of this result is provided in the appendix.