Subkey removed by 'delkey' command in interactive mode (gpg --edit-key) could be fully recovered by importing only it's public part - thus I suppose that the 'delkey' command removes only its public part and make the private part completely invisible but still present.

Steps to reproduce:
Machine one (with all the subkeys, including secret part of the master key)

gpg --export-secret-subkeys MY_SUB_NUM! > my_sub_key.asc
gpg --export > all_the_keys.asc

Machine two (with freshly installed gpg v 2.1.2, no keys present)

gpg --import all_the_keys.asc
gpg --import my_sub_key.asc
gpg --edit-key MY_KEY
        > key NUMBER_OF_MY_SUBKEY
        > delkey
        > save
gpg --import all_the_keys.asc

After these steps, i would expect to have only public part of MY_SUB_NUM, but I have both and I'm fully capable of signing etc.. There is no '#' after 'ssb' in the output of gpg --liste-secret-keys. If it is intentional behaviour of 'delkey' command I would expect it to be written in the doc at least..