Actually RFC's themselves contain references to each other with the space.

> hi  all rfc refs in all man pages use
> "RFC<space>XXXX".
> 
> jmc
> 
> On 13 December 2024 16:21:38 GMT, Theo de Raadt <deraadt@openbsd.org> wrote:
> 
>  Claudio Jeker <cjeker@diehard.n-r-g.com> wrote:
> 
>  One nit is that you mix RFC8538 and RFC 8538, it would be nice to stick
> to one spelling.
> 
> Yes. Undecided which way I should spell RFC references. I think I should
> walk over the tree and make all RFC8538 (without the space). What you
> think?
> 
> I agree.  I always write
> 
>   BIKESHED
> 
> rather than
> 
>   BIKE SHED
>