The current manual page structure is that, in the ERRORS sections, there are multiple "sub-sections" that are exclusive (most concern one function, one concerns both jail_attach() and jail_remove()) except for the last paragraph, which explicitly is an addition concerning three functions that refers the reader to another manual page (chroot(2)).

A priori, I don't want to inline the errors from chroot(2) here, as the list is relatively long, and anyway is common to three of the described functions (repeating it for each one would be very verbose), and because that would open the risk of the lists here and there becoming inconsistent.

My goal, however, is to save readers from having to open chroot(2) for the in-diff-added particular reason of returning EPERM, as this one is very much unintuitive and as such deserves to be mentioned inline.

Are you saying you'd like the added mention be structured like the other "sub-sections", i.e., with .Bl? Or do you want a more profound reorganization?