(ok, it's not actually incomprehensible to me as i've been reading the source code, but it would certainly confusing to a new user).
`--use-keyboxd` is included in `gpg --dump-options` (fixed from mistaken `--list-options`, sorry!) , which means that [commonly used tab-completion scripts](https://github.com/scop/bash-completion/blob/main/completions/gpg) will make it discoverable.
But when a novice user tries it they, get a strange note:
```
0 dkg@bob:~$ gpg --use-keyboxd --list-keys
gpg: Note: Please move option "use-keyboxd" to "common.conf"
0 dkg@bob:~$
```
Yes, it's interpretable if the user sifts through several different parts of the manpage and already understands common unix conventions; but it's noisy, and it seems likely to obscure real warnings that the user should be made aware of.
At the very least, GnuPG should hide `--use-keyboxd` from the output of `--list-options` so that it's not discoverable through tab-completion. But perhaps it shouldn't be accessible from the command line at all, if it is intended to *only* be meaningful in `~/.gnupg/common.conf`. If `gpg` needs to produce a warning when the option is given on the command line, while still interpreting it, the warning should identify the specific `common.conf` that the user needs to add it to (e.g. `/home/dkg/.gnupg/common.conf`), not just `common.conf`. Also, if `use-keyboxd` is already set in the appropriate `common.conf` maybe the warning isn't needed, as it should be a no-op?