staff_request_comments and reply_date in koha-conf.xml are only used in _censor method in Koha::Illrequest but this _censor method is not used anywhere else in Koha. Bug 19822 aims to move ILL config from koha-conf.xml into system preferences, but would it make sense to move configs that are not being used anywhere? Some ILL backends may use these, but all that I have checked so far do not. Backends maintained by PTFS-Europe do not use these. Tomas has confirmed the backends he maintains do not use these. Asking others in the community for confirmation and opinion on this.
I guess Tomas' check included ours, but I can confirm we don't use it.