should we add a section in the manual with deprecated items or have xboard output a warning/error when those items are used? I would prefer that instead of just deleting them.
It depends on what you mean by 'deprecating'. I don't consider removing undocumented options as deprecating anything. XBoard already gives an error message on using non-existent options. We did not deprecate any options recently. There seem to be some options in the list for things that were deprected some 15 years ago, and I didn't even propose to remove those. Just to not add their description to the manual. As far as I am concerned the synonyms using hyphen for negation are not very harmful either; I was just puzzled why we would have synonyms that are not documented anywhere, with equally long names as the documented versions.
