On 2013–01–07 Hans Hagen wrote:

> >The wrong \in[invalid] reference receives an easy to find error
> >marker and an entry in the log file. The wrong entry \in[sec:bar] is
> >hard to find.
> >
> >Is there a way to add ?? for those cases as well?
> 
> I'll print an !! although it might become optional

That's totally fine with me. Optional means one can turn it on and
off, perfect.

> at some point if I find that it has unwanted side effects.

Using \in with numbering turned off has side-effects, too ;)

Thanks Hans!

Marco